Diesel Engines H2 (Set 2) no

37. Technician A says that extended life coolants (ELCs) are premixed and should not be diluted with water. Technician B says that silicone radiator hoses should have special clamps. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D10)

Question #37 Answer C is correct. Both Technicians A and B are correct. ELCS are premixed and should not be diluted. Silicone hoses should have clamps designed for them and should be carefully torqued, since silicone hoses may be damaged by overtightening. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

47. Technician A says before installing die-cast rocker covers on a cylinder head, ensure a silicone gasket is coated with adhesive. Technician B says to always use new gaskets when installing valve covers. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C1)

Question #47 Answer D is correct. Neither technician is correct. When installing silicone gaskets into a rocker housing cover, the manufacturer service instructions should be observed. Answer A is incorrect. Technician A is incorrect because installing silicone gaskets into a rocker housing cover will seldom involve applying adhesive to the gasket. Answer B is incorrect. Technician B is incorrect. Many rocker housing gaskets on modern engines are designed to be reused and their price reflects this. Answer C is incorrect. Neither technician is correct.

71. Technician A says that high-pressure fuel lines should be bled of any air that might be trapped after replacement. Technician B says you can check for air in the fuel subsystem by installing a diagnostic sight glass and look for bubbles. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F1.3)

Question #71 Answer C is correct. Both Technicians A and B are correct. If necessary, purge the high-pressure fuel lines of air by loosening the connector one-half to one turn and cranking the engine until fuel, free from bubbles, sprays from the connection. Checking for air being pulled into the fuel subsystem is a good method as this is especially important when working with fuel subsystems that are entirely under suction. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

88. All of the following must be checked before installing rocker arms, EXCEPT: A. rocker arm bushings for wear B. rocker arm shaft for wear C. rocker arm pallet for pitting or scoring D. rocker arm adjustment screws are down (B8)

Question #88 Answer D is correct. When installing rocker arms, the bushings, shaft, and pallet (actuation end) must be inspected. However, the adjustment screws are not adjusted until the valve lash is set, which happens after the assembly. Answer A is incorrect. Rocker arms are checked prior to installing. Answer B is incorrect. The rocker shaft is inspected prior to installation. Answer C is incorrect. The pallet is inspected prior to reassembly.

1. In the internal shutdown solenoid in the figure, Technician A says that it must be tested after replacement. Technician B says to clean the old gasket off the cover and fuel pump when changing the shutdown solenoid. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F1.6)

Question #1 Answer C is correct. Both Technicians A and B are correct. Any component after replacement should be tested. Whenever a distributor-type fuel pump is opened up, the gasket surfaces should be cleaned and the components reassembled with new gasket. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

10. Technician A says that EUI calibration codes are indicated on each EUI and may be 2, 3, or 4 numeric digits depending on the manufacturer. Technician B says that calibration codes must be programmed to the ECM each time EUIs are replaced. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F24)

Question #10 Answer C is correct. Both Technicians A and B are correct. Calibration codes (bench fuel rates) are indicated on replacement EUIS. These codes should be programmed to the engine management ECM each time they are replaced. EUIS are graded with a calibration code. which enables the ECM to be programmed with data concerning how a specific EUI flows fuel. The diagnostic data reader (DDR) is used to program this data to the ECM and enables highly accurate and balanced fueling of the engine. lo program the calibration code, the injector cylinder number would be selected first followed by entering the digital calibration code value Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

100. The figure shows a sequence of numbers. These numbers are used for what purpose? A. to tell the technician which bolts to put in first B, to identify the torque sequence C. the serial number of the head D. the part number of the head (B7)

Question #100 Answer B is correct. The figures with this question show some typical torque sequence templates that the technician should observe when torquing cylinder heads. You will notice that the sequence starts in the middle to provide an even distribution of clamping force. This illustrates how the clamping force moves out from the middle when you tighten a cylinder head. The objective of torquing cylinder head gaskets is to ensure that the required amount of clamping force is obtained and the gasket conforms to its engineered yield shape. Some OEMS use the torque-turn method of clamping down the cylinder head. You initially torque the head to a small increment, such as 20 ft.-lb., then follow this torque up with a 90° (one-quarter) turn. Answer A is incorrect. This numbering shows the torque sequence. Answer C is incorrect. The serial number is stamped into the casting. Answer D is incorrect. The part number is cast into the head.

101. The throttle position sensor is being adjusted on an engine with electronic controls. Technician A says that on some applications the throttle position sensor produces a PWM (pulse width modulated) return signal. Technician B says the software will indicate when the setting is too low or too high. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.9)

Question #101 Answer C is correct. Both Technicians A and B are correct. Some throttle position sensors are designed to output a digital PWM signal to the ECM. TPS calibration can be guided by the manufacturer software so that mechanical pedal travel can be phased with the signal produced. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

102. Technician A says that testing the oil cooler bundle should be done at PM intervals. Technician B says that testing the oil cooler bundle is done as part of an engine overhaul. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D4)

Question #102 Answer B is correct. Only Technician B is correct, Testing an oil cooler bundle should be undertaken at a major engine overhaul and would not be a part of routine PM scheduling. Answer A is incorrect. The oil cooler bundle does not need to be tested at every PMI. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

103. In the setup shown in the figure, what is being checked on the flywheel housing? A. lateral runout B. face lateral runout C. radial runout D. pilot bore radial runout (C18)

Question #103 Answer C is correct. The figure shows the flywheel housing being checked for radial runout. This is a critical measurement that should be performed whenever a flywheel housing is removed and reinstalled from the engine block. If this measurement is out of specification, the result can be crankshaft damage, engine mount damage, flywheel housing damage, and transmission failures. Answer A is incorrect. This is not the lateral runout test. Answer B is incorrect. The dial indicator is not on the housing face. Answer D is incorrect. The dial indicator is not on the pilot bore.

104. Technician A says "lugging" occurs when the accelerator is in full fuel position and the engine cannot pick up speed under load. Technician B says air starvation results in low cylinder temperatures. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A1)

Question #104 Answer A is correct. Only Technician A is correct. Some possible causes of high pyrometer readings are: air inlet restriction, flow restricted, boost air heat exchanger, high engine load, fuel injection timing, and overfueling. Answer B is incorrect. Air starvation does not result in lower cylinder temperatures. In fact, the temperatures would be higher, not lower. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

105. A fuel pump with a mechanical variable speed governor does all of the following EXCEPT: A. controls idle speed B. meters fuel to the injectors C. regulates maximum engine speed D. prevents engine lug (Fl.6)

Question #105 Answer D is correct. A mechanical variable-speed governor has no way of keeping the operator from lugging the engine. It sets engine idle speed and defines high idle and any speed in the intermediate range, depending on accelerator pedal position. A given amount of accelerator pedal travel will correspond to an engine rotational speed. As engine loading either increases or decreases, the governor will manage fueling to attempt to maintain that engine speed. Hydromechanical variable speed governors were common in many Mack Trucks and Caterpillar applications, among others, where power take-off (PTO) management was a consideration. PTO management is used when the engine drives auxiliary equipment. From the driver perspective, the VS governor takes a little getting used to. Most of today's electronic management systems can be toggled to either LS or VS mode. A governor classified as variable speed will usually provide excess startup fuel, define a torque rise profile, define droop curve, and be capable of no-fueling the engine for shutdown. Answer A is incorrect. A mechanical variable speed governor controls idle speed. Answer B is incorrect. A mechanical variable speed governor does meter fuel to the injectors. Answer C is incorrect. A mechanical variable speed governor does control maximum engine speed.

106. Tech A says dash gauges provide better information than warning lights because you can see when they are not working. Tech B says failure of a digital or electronic gauge may not be fault of the actual gauge circuit. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D1)

Question #106 Answer C is correct. Both Technicians A and B are correct. Dash gauges are a better indicator of imminent problems than dash warning lights because they are capable of monitoring a worsening condition, giving the driver some advanced warning of a failure. Gauge failures can be caused by conditions other than the gauge circuit. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

107. Tech A says that om a HEUI fuel system, high-pressure engine oil is used as hydraulic medium to actuate the injector fuel pump stroke. Tech B says that because the engine ECM controls the actuation oil pressure in a HEUI system, the rate of injecting fuel can be precisely controlled. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.3)

Question #107 Answer C is correct. Both Technicians A and B are correct. Technician A correctly describes the actuation medium in a HEUI injector. Also, HEUI injectors are capable of rate shaping; that is, precisely defining the speed at which the fuel injection plunger is driven into the pump chamber by managing the actuation oil pressure. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

108. When performing a load test on a fully charged battery, the technician find that the battery voltage drops below manufacturer's specifications. The technician should do which of the following? A. recharge the battery and return it to service B. recharge the battery and retest it C. replace the battery D. replace the voltage regulator (G2)

Question #108 Answer C is correct. Before a load test is performed on a battery, some specific criteria have to be met, including having the battery properly charged. If the battery then fails the load test, it should be replaced. The load, or capacity, test determines how well any type of battery, sealed or unsealed, functions under a load. Answer A is incorrect. If the test was performed correctly, then the battery was already adequately charged. Answer B is incorrect. The battery was fully charged before the test, therefore charging the battery a second time will not change the results of the test. Answer D is incorrect. There is no reason to believe the voltage regulator is faulty; even if it is, replacing the regulator will not fix a faulty battery.

109. While discussing a computer-controlled diesel engine, Technician A says corrosion on wiring connectors can affect engine performance. Technician B says that after repairing sealed wire connectors, they should be treated with a corrosion inhibitor. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.6)

Question #109 Answer A is correct. Only Technician A is correct. Corrosion on wiring connectors on computer-controlled engines can affect engine performance and cause codes to be logged. Answer B is incorrect. Many terminals on vehicle electronic system wiring harnesses are manufactured out of materials such as gold and platinum to provide reliable continuity and corrosion resistance. Unless the manufacturer recommends treatment of terminals and connectors with a corrosion inhibitor, it should not be used. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

11. Technician A says that manufacturers allow for relative movement between the chassis and the engine by using durable rubber couplings in the intake system. Tech B says that if an air intake pipe, tube, or hose is loose or missing a clamp, the turbocharger compressor should be inspected. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (E1)

Question #11 Answer C is correct. Both Technicians A and B are correct. The relative movement between the intake take System components on the chassis and those on the engine must be accommodated by having flexible rubber couplings. The smallest leak in the intake system components can allow dirt congestion by the turbocharger and engine so the turbocharger should first be inspected, If the turbocharger is found to be damaged, the engine should also be inspected. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

110. In the figure, what adjustment is being performed? A. valve bridge/yoke balance B. valve lash C. injector timing D. injector hold-down (B6)

Question #110 Answer A is correct. The figure shows the adjusting of a valve yoke or bridge. The valve yoke is actuated by the rocker and valve lash is defined at the rocker adjusting screw. The adjustment shown ensures that both valves are actuated at exactly the same moment. Answer B is incorrect. Valve lash is not adjusted with this screw. Answer C is incorrect. The injectors are not shown in this figure. Answer D is incorrect. The injector hold-down is not shown in this figure.

111. Technician A says a micrometer can be used to measure the crankshaft journals. Technician B says that when cleaning crankshaft journals, a wire wheel on a die grinder can be used. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C8)

Question #111 Answer A is correct. Only Technician A is correct. A micrometer is commonly used to measure crankshaft journals. Answer B is incorrect. Most diesel engine manufacturers would disapprove of using a wire wheel to clean up crankshaft journals. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

112. Technician A says the starter ring gear should be replaced if damaged teeth are found. Technician B says the flexplate bolts directly to the crankshaft, Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C18)

Question #112 Answer C is correct. Both Technicians A and B are correct. Starter ring gears should be checked for damaged teeth, and replaced if damage is present. Vehicles with automatic transmissions use flexplate assemblies that bolt to both the torque converter and the crankshaft directly. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

113. Technician A says ethylene glycol (EG) and propylene glycol (PG) should not be mike Technician B says if switching the type of antifreeze used, the cooling system must be flushed completely first. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D10)

Question #113 Answer C is correct. Both Technicians A and B are correct. EG and PG should never be mixed because they are chemically incompatible and once mixing has taken place, it becomes impossible to measure the extent of antifreeze protection provided by the coolant. The mixture in itself will not cause any engine or cooling system problems, but it will be impossible to determine the antifreeze mixture strength with either a refractometer or a hydrometer. If a mixture of EG and PG is known to have taken place and the coolant, for whatever reasons, cannot be immediately replaced, use a refractometer with an EG and a PG scale and average the two readings. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

114. Which of the following must the technician do first after dry cylinder liners are removed A. main bearing caps must be inspected B. lock bores must be inspected C. oil ports must be inspected D. cam bearing bores must be inspected (C4)

Question #114 Answer B is correct. In this sequence, the technician should inspect the cylinder block bores first after a set of dry liners is removed. Sleeves should be removed with a puller and adapter plate or shoe. The procedure is obviously more simple on wet liners. Dry sleeves often require the use of mechanical, hydraulic, or air-over-hydraulic pullers. When these fail to extract a seized liner, vertical arc weld runs may break a liner free, but great care has to be exercised because the block may become distorted. To use this method of removing a seized liner, first ensure that every critical engine component is moved well out of the way, then use two vertical-down runs with an E6010/11 electrode at 90° from the piston thrust faces. Shock cool the welds with cold water and attempt to use the puller again. Avoid fracturing seized liners out of their bores as this practice almost always results in bore damage. As a last resort, liners can be machined out using a boring jig. Answer A is incorrect. Main bearing caps can be left in place. Answer C is incorrect. Oil ports do not need to be inspected immediately after liner removal. Answer D is incorrect. Cam bearing bores are not necessarily inspected immediately after liner removal.

115. A vehicle has been found to have excessive dirt in the fuel filters. Technician A says to change the filters and return the vehicle to service. Technician B says in addition to servicing the filters, the fuel tank should be drained and flushed. Who is correct? A. A only B. B only C. Both A and B D. Neither A or B (A6)

Question #115 Answer B is correct. Only Technician B is correct. If excessive contaminants are found in the fuel filters, the source of the contamination needs to be identified and corrected. If the source is the vehicle fuel tank, the tank should be drained, and flushed of the contamination. Answer A is incorrect. The source of the contamination should be corrected before the vehicle is returned to service; otherwise the filters will only clog again. C is incorrect. Only Technician B is correct. D is incorrect. Only Technician B is correct.

116. Technician A says that electronic connectors should never be probed through the weather-pack seals. Technician B says a breakout box or T should be used to test connectors. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.6)

Question #116 Answer C is correct. Both Technicians A and B are correct. Electronic connectors should never be probed for any reason. Breakout boxes and Ts are commonly used to test electronic circuits in modern vehicles. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

117. Which of the following should the technician check first when installing a cylinder head to the engine block? A. bolt holes for foreign matter and cross threading B. head bolt torque C. rocker pedestal height D. valve bridge adjustment (B7)

Question #117 Answer A is correct. The bolt holes should be checked first; the remaining procedures are performed after the cylinder head has been installed. On in-line multi cylinder heads, it is usually required that separate heads be aligned with a straightedge across the intake manifold faces before torquing. Failure to observe torquing increments and sequencing can result in cracked cylinder heads, failed head gaskets, and fire rings that will not seal. Cylinder head bolts should be installed lightly oiled. Excessive quantities of oil should be avoided because the excess can drain into the bolt hole and cause a hydraulic lock. Answer B is incorrect. Head bolts are torqued after installation. Answer C is incorrect. Rocker pedestals are checked after head installation. Answer D is incorrect. Valve bridges are adjusted after installation.

118. A 4-stroke cycle diesel engine has vibration occurrence rate that is equal to half the engine rpm. Technician A says that this might e caused by a bent camshaft. Technician B says that this could be caused by a bent connecting rod. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A13)

Question #118 Answer A is correct. Only Technician A is correct. When a vibration occurrence rate seems to be half the engine speed, check the camshaft and cam trains first because the camshaft is rotated at half engine speed. Technician A is correct in suspecting a bent camshaft. Answer B is incorrect. A bent connecting rod would produce a vibration incidence that would correlate with engine speed. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

119. In the figure, what force is used to create injection pressure values? A. hydraulic B. electronic C. electromechanical D. mechanical (F2.3)

Question #119 Answer A is correct. The figure shows a hydraulically actuated, electronic unit injector. These injectors are actuated by high-pressure engine oil. Answer B is incorrect. Electronics simply open or close an oil passage. Answer C is incorrect. Electromechanical would be a EUI-style injector. Answer D is incorrect. A mechanical injector would have no electronics associated with it and would not be pressurized by oil.

12. All of the following are corect procedures if a pressure cap is found to be defective EXCEPT: A. replace the cap B. test the coolant C. check the radiator hoses D. adjust or replace the spring in the cap (D13)

Question #12 Answer D is correct. If a radiator cap is tested to be defective, replace the cap, test the coolant, and check the radiator hoses for leakage and collapsing. Attempting to adjust or replace the spring is not good practice. Answer A is incorrect. The cap should be replaced. Answer B is incorrect. The coolant should be tested. Answer C is incorrect. The radiator hoses should be checked.

120. A diesel ECM has logged both active and inactive codes. Technician A says that both the active and inactive codes can be erased providing the manufacturer's diagnostic software is used. Technician B says that both active and inactive codes produce fault mode indicators (FMIS), which permit them to be accessed by any diagnostic instrument capable of reading SAE codes. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.1)

Question #120 Answer B is correct. Only Technician B is correct. When a code is produced so is a fault mode indicator (FMI), which can be read by diagnostic instruments capable of reading SAE codes. Answer A is incorrect. Technician A is incorrect. Active codes can never be erased because the fault is currently occurring. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

121. Technician A says if the turbocharger lines and hoses become frayed or nicked, they must be replaced not repaired. Technician B says turbocharger oil tubes must be checked for obstructions. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (E2)

Question #121 Answer C is correct. Both Technicians A and B are correct. When turbocharger lines and hoses become nicked or frayed, it is good practice to replace them rather than repair them, so Technician A is correct. Technician B is also correct because it is good practice to inspect oil tubes for damage before returning them to service. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

122. Technician A says overfueling can cause black smoke emission. Technician B says that soot in the combustion chamber can cause this problem. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A5)

Question #122 Answer A is correct. Only Technician A is correct. Overfueling causes black smoke emission, essentially soot caused by partially combusted fuel. Answer B is incorrect. Coolant in the combustion chamber condenses in the exhaust and is emitted as white smoke. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

123. A vehicle is equipped with a serial bus dash. All gauges read erratic. The ECM has not turned on the check engine lamp. Which of the following is the Most-Likely cause? A. faulty dash B. faulty alternator C. a faulty oil pressure sensor D. a faulty oil pressure gauge (D1)

Question #123 Answer A is correct. The dash is most likely faulty. Answer B is incorrect. Since the signal to the dash is feed off the data bus, the alternator is not the Most-Likely cause of the problem. Answer C is incorrect. A faulty oil pressure sensor would effect only the oil pressure gauge, and it should also set a DTC in the engine ECM. Answer D is incorrect. A faulty oil pressure gauge would only effect the oil pressure gauge, not the whole dash.

124. What should the battery's electrolyte temperature not be allowed to exceed during the "fast charge" method? A. 125°F B. 200°F C. 100 F D. 150°F (G3)

Question #124 Answer A is correct. 125°F is the cut-off point for electrolyte temperature during charging. Exceeding this temperature can result in battery damage or explosion. Answer B is incorrect. That is above 125°F Answer C is incorrect. That is below 125°F Answer D is incorrect. That is above 125°F

125. While inspecting an electrical connector for damage, the connector lock tab is found to be broken off. Technician A says to use a wire-tie to secure the connector. Technician B says to replace the connector and install new terminal pins, Who is correct? A. A only B. B only C. Both A and B D. Neither A or B (F2.7)

Question #125 Answer D is correct. Neither technician is correct. Answer A is incorrect. Technician A is incorrect. If connectors are damaged in any way, they should be replaced. Securing with a wire-tie is poor practice. Answer B is incorrect. Technician B is incorrect. While the damaged connector should be replaced, the terminal pins should be inspected to determine if replacement is necessary. Terminal pin replacement is not necessary to replace the connector in most cases. Answer C is incorrect. Neither technician is correct.

126. When installing the wrist pin retaining snap rings in an articulating piston assembly, what is most commonly the recommended position of the snap ring gap? A. downward B. upward C. horizontal D, does not matter (C11)

Question #126 Answer A is correct. Most manufacturers recommend that the snap ring gap be in the down position. Most important, it is never located at 90° to the direction of travel. All full-floating piston pins require a means of preventing the pin from exiting the pin boss and contacting the cylinder walls. Snap rings and plugs are used. When installing the internal snap rings used by most engine OEMS, observe the installation instructions. Answer B is incorrect. The ring gap should not go up. Answer C is incorrect. The ring gap should not go horizontal; this will allow inertia forces the opportunity to loosen the ring. Answer D is incorrect. It does matter where the ring gap is installed.

127. A vehicle has higher than nornal fuel pressure. Which could be the Most-Likely cause? A. a broken regulator valve spring B. a blocked fuel tank vent C. a stuck regulator valve piston D. aerated fuel (F14)

Question #127 Answer C is correct. For the regulator to maintain a desired fuel pressure limit, the valve be able to move in its bore, bleeding off excess pressure. If the valve was seized in the bore. The pressure can build to higher than normal pressure. Answer A is incorrect. A broken valve spring would cause lower than normal fuel pressures Answer B is incorrect. A fuel tank vent controls air pressure in the fuel tank, not pump pressure. Answer D is incorrect. Aerated fuel usually causes low fuel pressures.

128. A vehicle is being diagnosed for white smoke on cold weather startups. When the master switch is turned on, the Wait To Start" lamp illuminates and goes out, but when the engine is started it emits white smoke. Technician A says the heater grids should be checked with an ohmmeter. Technician B says the heaters are controlled by relays, and the relays should be replaced, Who IS correct? A. A only B. B only C. Both A and B D. Neither A nor B (E6)

Question #128 Answer A is correct. Only Technician A is correct. Since the "Wait To Start" lamp is illuminating, the ECM is commanding the heater grids on. The heater grids themselves may be suspect, so they should be tested against manufacturer's specifications. Generally, the grids will be checked for a specific resistance value. Technician A is correct. Answer B is incorrect. The ECM controls the heater grid(s) with relay(s), but the relays should be tested for proper operation before they are replaced. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

129. While inspecting the exhaust system, the technician notices that the vehicle has excess exhaust back pressure. Which of the following is LEAST-Likely to cause this? A. improper muffler B. carbon build-up in the exhaust system C. collapsed exhaust pipe D. high exhaust temperature (A9)

Question #129 Answer D is correct. Improper muffler, carbon build-up in the exhaust system, and a collapsed exhaust pipe are all capable of causing high exhaust back pressures. High exhaust temperature in itself would unlikely cause increased back pressure values so this is the LEAST-Likely cause. Answer A is incorrect. An incorrect muffler can cause high EBP. Answer B is incorrect. Carbon build-up can cause high EBP. Answer C is incorrect. A collapsed exhaust pipe can cause high EBP.

13. Technician A says a loss of engine lubrication oil through the breather tube is an indication of excess crankcase pressure. Technician B says any measurable crankcase pressure is a sign of trouble. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A10)

Question #13 Answer A is correct. Only Technician A is correct. Loss of engine oil through a breather tube is a common indication of high crankcase pressure. Answer B is incorrect. Most current engines run with a specified crankcase pressure and, providing it is within specification, no problems are indicated. Because rings create the seal of a piston in a cylinder bore, some blowby is inevitable, due to end-gap requirement. Normally, blowby is a specification determined by the OEM. Piston rings seal most efficiently when cylinder pressures are highest, and engine rpm is high when there is less time for gas blowby. Some causes of high crankcase pressure are: • Cracked head or piston • Worn, stuck, or broken piston rings • Glazed liner/sleeve inside wall • Air compressor (plugged discharge line, air pumped through oil return line) • Turbocharger (seal failure allows turbine housing to leak pressurized air through to the turbine shaft and back through the oil return piping Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

130. When testing a cylinder head for potential coolant leakage, Technician A says the coolant needs to be heated to operating temperature. Technician B says the coolant needs to be under pressure. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B3)

Question #130 Answer C is correct. Both Technicians A and B are correct. Both technicians are describing the correct bench-test procedure for testing a cylinder head. A cylinder head should be heated to swell any cracks by flowing hot water through it for 10 minutes. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

131. A connector is found to be distorted from heat but when checked with an ohmmeter the electrical connection is still good. Tech A says to replace the connector. Tech B says to apply electrical tape around the connector. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.10)

Question #131 Answer A is correct. Only Technician A is correct. Any visibly damaged connector should be replaced. Checking an electrical connector with an ohmmeter is not a good indicator of how the connector will perform when the circuit is energized. Every technician should understand the importance of voltage drop testing and that means understanding the limitations of the ohmmeter. Ifa copper starter motor cable has deteriorated to the extent that only 10 percent of its wire strands remain intact, an ohmmeter measurement will indicate that it checks out with a resistance reading similar to that of a cable in perfect condition because the ohmmeter is forcing a minute current through the test circuit. However, if a voltage drop test were to be performed on the cable while cranking the engine, the voltage dropped would immediately indicate the problem. Answer B is incorrect. Placing electrical tape around the damaged connector is bad practice. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

132. In the fan assembly shown in the figure, Technician A says that fan bearings should be submerged in cleaning solvent and air-dried. Technician B says because fan bearings are water-cooled some corrosion is acceptable, although if corrosion is excessive they should be replaced. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D14)

Question #132 Answer A is correct. Only Technician A is correct. Fan drive hub assemblies must be inspected. Clean the fan and related parts with clean solvent and dry them with compressed air; do not spin dry the bearings. Shielded bearings must not be washed as dirt may be washed in, and the cleaning fluid could not be entirely removed from the bearing. Examine the bearings for any indications of corrosion or pitting. Hold the inner race or cone so it does not tum, and revolve the outer race or cup slowly by hand. if rough spots are found, replace the bearings. Technician A is correct in describing how the fan bearings should be cleaned. Answer B is incorrect. The fan bearings are not water-cooled. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

133. Which of the following is LEAST-Likely to be the cause of a electronic unit injector (EUI) diesel engine not starting? A. excessive exhaust back pressure B. short in the starter armature C. corrosion on battery terminals D. low engine lube level (A11)

Question #133 Answer D is correct. The LEAST-Likely cause of a failure to start an engine would be a low lubricant level. Low lube levels can result in significant engine damage. Although low oil levels can result in low oil pressure and engine shutdown, oil pressure and level-sensor inputs are ignored until after the engine starts. Answer A is incorrect. Excessive exhaust back pressure could cause an engine to fail to start. Answer B is incorrect. A short in the starter armature would cause slow cranking speed, which could cause the engine to fail to start. Normal minimum cranking speed is 100-200 rpm. Answer C is incorrect. Battery terminal corrosion can cause slow cranking speed and a failure of the engine to start.

134. An engine is being overhauled because of a broken crankshaft. Technician A says the operator could have been overspeeding the engine. Technician B says an out-of-round condition may exist on one or more of the main bores. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A1)

Question #134 Answer C is correct. Both Technicians A and B are correct. Engine overspeed can cause a crankshaft failure as can out-of-round main bearing bores. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

135. Technician A says that with a wet sleeve-type cylinder, the cylinder only seals at the top. Technician B says in this type of liner the coolant comes into direct contact with the liner. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C3)

Question #135 Answer B is correct. Only Technician B is correct. The O-rings used to seal wet liners are made from a variety of rubber-type compounds. It is important that OEM installation recommendations be observed. They may be installed dry, coated in coolant, soap, engine oil, and various other substances. Wet liners are often alloyed so they possess characteristics metallurgically superior to the block casting, which increase service life. Answer A is incorrect. Wet sleeves or liners come into direct contact with coolant in the water jacket so they must seal top and bottom. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

136. Technician A says that an oil residue on the inside of the engine door may indicate excess crankcase pressure. Technician B says that oil on the exhaust joints could indicate a turbocharger oil seal failure. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A2)

Question #136 Answer C is correct. Both Technicians A and B are correct.Excessive crankcase pressure can form an oily film on the inside of the engine door. If a turbocharger oil seal failure is present, oil can sometimes be seen on the exhaust joints. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

137. When removing an internal shutdown solenoid from a rotary distributor pump, what must the technician remove first? A. the solenoid cover B, the pump cover C. the injector pump D. the control module (Fl.6 and F2.5)

Question #137 Answer B is correct. When removing the internal shutdown solenoid from a distributor type pump, the pump cover has to be removed to access the solenoid. Answer A is incorrect. This style of shutdown solenoid does not have a solenoid cover. Answer C is incorrect. The injector pump normally does not need to be removed for this repair. Answer D is incorrect. The control module would not need to be removed for this repair.

158. All of the following are components in the valvetrain EXCEPT: A. rocker B. push tube C. cam follower D. cam plug (B1)

Question #138 Answer D is correct. The cam plug seals the rear of the camshaft so this is not part of the valvetrain. Answer A is incorrect. The rocker is part of the valvetrain. Answer B is incorrect. The push tube (rod) is part of the valvetrain. Answer C is incorrect. The cam follower (lifter) is part of the valvetrain.

139. After replacing the injector sleeve as shown in the figure, Technician A says the injector tip height must be checked. Technician B says to perform a cylinder head leakage test. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B5)

Question #139 Answer C is correct. Both Technicians A and B are correct. Whenever injector sleeves or tubes are replaced, it is essential to check the installed injector tip protrusion to verify whether the sleeve has been properly installed in the cylinder head. Because the injector sleeve/tube comes into direct contact with coolant it is also good practice to perform a cylinder head, pressure leakage test (hydrostatic) to ensure there are no leaks. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

14. Technician A says pistons should be laid out in order to facilitate failure analysis. Technician B says installing an improper injector nozzle could cause piston failure. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C11)

Question #14 Answer C is correct. Both Technicians A and B are correct. Good failure analysis is key to avoiding repeat failures. Technician A's method of organizing disassembled pistons is good practice. Improper injectors can cause a variety of piston failures, so Technician B is also correct. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

140. A diesel engine that has a low power problem could be caused by all of the following EXCEPT: A. restricted air filter B. leaking fuel line C. restricted fuel filter D. missing air filter (A12)

Question #140 Answer D is correct. While a missing air filter can result in serious damage, this would have little limiting effect on power produced until the damage was caused, so this is the LEAST-Likely cause. Answer A is incorrect. A restricted air filter would cause low pressure Answer B is incorrect. A leaking fuel line would cause low power. Answer C is incorrect. A restricted fuel filter would limit the amount of fuel the engine gets, resulting in low power.

141. Technician A says that valve crosshead guide pins should be at right angles to the cylinder head milled surface. Technician B says to check the crosshead guide pin diameter with a micrometer, and compare it to manufacturer's specifications. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B6)

Question #141 Answer C is correct. Both Technicians A and B are correct. Crosshead guide pins must be perfectly set at right angles to prevent side loading of the valves by the bridge, so Technician A is correct. Technician B is also correct in saying that crosshead guide pins should be measured to specification with a micrometer. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

142. An engine fails to achieve normal operating temperature. Technician A says that a stuck thermostat could cause this problem. Technician B says that an overfilled radiator could cause this problem. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A14)

Question #142 Answer A is correct. Only Technician A is correct. Ifa thermostat is stuck in the open position, it can cause an engine to fail to reach the normal operating temperature window. Answer B is incorrect. An overfilled radiator tank is unlikely to prevent an engine from reaching its normal operating temperature. It would most likely result in coolant being sent to the recovery bottle. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

143. Technician A says misalignment between pulleys must not exceed 1/16 in. (1.59 mm) for each 12 in. (30.5 cm) of distance between pulley running centerlines. Technician B says belts must not touch the bottom of grooves or protrude more than 332 in. (2.38 mm) above the top of the groove. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D12)

Question #143 Answer C is correct, Both Technicians A andB are correct.. The alignment specifications for pulley-running centerlines as described are correct. Pulley belts should also not contact the bottom of the pulley grooves. • When two or more identical belts are used on the same pulley, all of the belts must be replaced at the same time. • Make sure the distance between the pulley centers is as short as possible when you install the belts. Do not roll the belts over the pulley. Do not use a tool to pry the belts onto the pulley. • Pulleys must not be out of alignment more than l/16 in. (1.59 mm) for each 12 in. (30.5 mm) of distance between the pulley center. • Belts must not touch the bottom of the pulley grooves, and they must not protrude more than 3/32 in. (2.38 mm) above the outside diameter of the pulley. • When identical belts are installed on a pulley, the protrusion of the belts must not vary more than 1/16 in. (1.59 mm). • Make sure that the belts do not touch or hit any part of the engine. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

144. When the accelerator pedal on an electric foot pedal assembly (EFPA) is moved from 0 to full travel, the throttle position sensor (TPS) should indicate A. 0 VDC to 5 VDC. B. 5 VDC to 0 VDC. C. 0.5 VDC to 4.5 VDC. D. 4.9 VDC to 0.2 VDC. (F2.2)

Question #144 Answer C is correct. The throttle position sensor, a potentiometer, receives V-Ref, usually 5 VDC, and returns a portion of that voltage as a signal depending on accelerator pedal angle. To verify that the signal produced has actually passed through the sensor (as opposed to an open or shorted signal), they are designed to produce as a signala small voltage value at 0 pedal travel and always less than V-Ref at maximum pedal travel. Typically, this would be the values indicated in Answer C. Answer A is incorrect. The very ends of the voltage range 0 volts or 5 volts would indicate an open or short. Answer B is incorrect. Nearly all TPS signals start low at 0 throttle and work their way up at higher throttle. Answer D is incorrect. Nearly all TPS signals start low at 0 throttle and work their way up at higher throttle.

145. Which would LEAST-Likely be caused by incorrectly aligning the flywheel housing? A. rear oil seal failure B. broken flywheel bolts C. transmission damage D. U-joint failure (C17)

Question #145 Answer D is correct. U-joint failure is usually caused by driveshaft problems, and would be unaffected by the flywheel housing alignment. Answer A is incorrect. Rear oil seal failure can be caused by improper flywheel alignment. Answer B is incorrect. Flywheel bolt breakage can be caused by improper flywheel alignment. Answer C is incorrect. Transmission damage can be caused by improper flywheel alignment.

146. Troubleshooting has indicated that a thermistor-type coolant temperature sensor is not returning a signal voltage. Which of the following should be done first? A. Check the V-Ref value. B. Consult the manufacturer's service literature. C. Simulate V-Ref to check for signal voltage. D. Check thermistor internal resistance using an ohmmeter. (D8)

Question #146 Answer B is correct. When troubleshooting electronic input circuit components, it is essential to consult the manufacturer's service literature. Answer A is incorrect. V-ref voltage check is not the first step. Answer C is incorrect. Simulating V-ref voltage would be much further down the troubleshooting tree; it would not be the first step. Answer D is incorrect. While checking resistance of the sensor would be an early troubleshooting action, it would not be the first step.

147. An operator complains the fuel gauge is always reading full, even after driving all day. Technician A says the sending unit in the tank may have failed. Technician B says the sending unit float may have a hole in it, and it is filled with fuel. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F1.1)

Question #147 Answer A is correct. Only Technician A is correct. Most gauges use the position of the sending unit to vary the ground to the gauge, with a full tank providing very little ground to the gauge, while an empty tank providing a good ground. If the circuit to the sending unit or the resistor has an open, the gauge will read full by default. Answer B is incorrect. If the sending unit float filled with fuel, it would sink to the bottom of the tank, resulting in a gauge reading of empty all the time. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

148. When removing a starter motor from a vehicle, what should the technician remove first? A. starter bolts B. starter solenoid C. battery ground cable D. starter magnetic switch (G6)

Question #148 Answer C is correct. Knowledge of a procedure is being tested in this question. You can bet that disconnecting the ground cable is going to be one of the first steps in any procedure involving the replacement of an electrical component, because this renders the chassis electrically neutral. Answer A is incorrect. The starter bolts would likely be the last step in removal. Answer B is incorrect. The solenoid is integral to the starter and does not need to be removed. Answer D is incorrect. The magnetic switch does not need to be removed with the starter.

149. Fuel injectors should be timed when A. the exhaust valves are open. B. the injector follower is fully depressed. C. the cylinder is at TDC of a compression stroke. D. excessive valvetrain noise is noticed. (B10)

Question #149 Answer A is correct. Generally, when the fuel injector timing is set, the injector should be in a static position when the cylinder is not on a compression stroke. If the position of the exhaust valves is open, the camshaft is 180° from firing the injector, and timing height can be set. Manufacturer's specifications and procedures should always be consulted first. Answer B is incorrect. If the follower is fully depressed, the injector is firing, and cannot be properly adjusted. Answer C is incorrect. If the cylinder is at TDC of a compression stroke, the injector is firing and cannot be properly adjusted. Answer D is incorrect. Excessive valvetrain noise is usually an indication of excessive valve clearance, not improper fuel injector timing.

15. When performing a valve adjustment on a diesel engine with valve bridges, Technician A says the valve bridges must be adjusted before the valve clearance is set. Technician B says the valve bridge adjustment locknuts should torqued with the bridges secured in a vice. Who is correct? A. A only B. B only C. Both A and B D. Neither A or B (B6)

Question #15 Answer C is correct. Both Technicians A and B are correct. The valve bridge must be adjusted before the valve clearance is set, since adjusting the bridge could affect the valve clearance. When torqueing the bridge locknuts, they should be removed from the engine and secured in a vice to prevent damage to the bridge guide pins and valves. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

150. Under load, a diesel engine emits dark black smoke from the exhaust pipe, What should the technician check first? A. air cleaner B. fuel pump C. injector pump D. turbocharger (A5)

Question #150 Answer A is correct. Whenever a diesel engine emits black smoke, oxygen starvation caused by air-cleaner restriction should be checked first, mainly because it can be checked and quickly eliminated as a cause. Test the intake air inlet restriction using a water manometer. Specifications should always be checked to the OEM values, but typical maximum values will be close to: • 15 inches H,0 vacuum naturally aspirated engines • 25 inches H,0 vacuum-boosted engines Answer B is incorrect. The fuel pump (transfer pump) is very unlikely to cause a black-smoke condition. Answer C is incorrect. The injector pump may cause black smoke, but it is not the first item to check. Answer D is incorrect. The turbocharger can cause black smoke, but it is not the first item to check.

151. All of the following could cause fuel to contaminate the engine oil EXCEPT: A. cracked fuel gallery in the head B. broken piston ring C leaking intake manifold gasket D leaking injector seal (A15)

Question #151 Answer C is correct. A leaking intake manifold gasket is the LEAST-Likely cause because it would not cause fuel to enter the lubrication oil. When fuel contaminates engine oil, the oil loses its lubricity and it appears thinner and blacker in color. The condition is usually easy to detect because small amounts of fuel in oil can be recognized by odor. When fuel is found in significant quantities in engine oil, the cylinder head(s) are the likely source, Answer A is incorrect. A cracked fuel gallery in a cylinder head could cause fuel to enter the lubricating oil. Answer B is incorrect. A broken piston ring could cause incomplete combustion, which could cause fuel to enter the lubricating oil. Answer D is incorrect. A leaking injector seal can cause fuel to enter the lubricating oil.

152. When removing a piston from an engine cylinder block, which of these should the technician do first? A. remove the crankshaft B. remove the piston wrist pin C. remove the carbon ridge D. remove the sleeve seals (C2)

Question #152 Answer C is correct. Before removing each piston and connecting rod assemblies, scrape carbon deposits (ring ridge) from the upper-inside wall of each cylinder liner using a ridge reamer. Answer A is incorrect. The crankshaft is not removed prior to the piston. Answer B is incorrect. The piston pin cannot be removed prior to the piston assembly. Answer D is incorrect. The cylinder sleeves are removed after the piston assembly.

153. The figure shows a sectional view of a typical electronic unit injector (EU). Technician A says that injection pressures are Created by mechanical force from the camshaft. Technician B says that actual injected fuel quantity is computer controlled by switching the control solenoid. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.6)

Question #153 Answer C is correct. Both technicians are correct. Electronic unit injectors (EUs) are mechanically actuated by an injector train and cam profile and metered fuel quantity is controlled by computer switching of the EUI solenoid. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

154. A thermostatically controlled fan, as shown in the figure, may rely on all of the following to regulate fan operation EXCEPT: A. a coil spring B. air temperature C. radiator temperature D. air pressure (D14)

Question #154 Answer D is correct. A coil spring, radiator temperature, and air temperature can all be used to regulate fan operation in a thermostatically controlled fan. Air pressure is not a factor in controlling fan cycling so this is the exception. Thermatic viscous drive fan hubs are integral fan drive units with no external controls. They use silicone fluid as a drive medium between the drive hub and the fan drive plate. Answer A is incorrect. This fan does use a coil spring. Answer B is incorrect. Air temperature does regulate this fan operation. Answer C is incorrect. Radiator temperature does affect this fan because radiator temperature affects the temperature of the air passing through it.

155. A fleet bus driver complains that his electronically managed engine will not reach rated engine pm when in the upper transmission gear ratios. Technician A says that there is a problem with the fuel map programming to the engine ECM, limiting top-end fueling. Technician B says that the engine electronics have been programmed with a progressive shifting profile designed to improve fuel economy. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.1)

Question #155 Answer B is correct. Only Technician B is correct. Technician B has identified the cause of the driver's complaint: progressive shifting has been programmed into customer data programming to improve fuel economy. Progressive shifting can assist less experienced drivers of buses by providing engine speed prompts during different vehicle speeds. Progressive shifting can make a significant difference to vehicle fuel economy. Answer A is incorrect. Technician A is incorrect. Fuel map programming is factory set and can only be changed when new calibration files are downloaded to the engine ECM. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

156. In the figure showing a typical EUI, what does the technician do to time the injector when the top end is set? A. adjust the rocker arm screw B. program the calibration codes to the ECM C. program the timing codes to the ECM D. adjust the cam follower assembly (F2.4)

Question #156 Answer A is correct. Timing an EUI requires the setting of the EUI plunger height, a mechanical adjustment performed by setting the rocker arm adjusting screw. Answer B is incorrect. Calibration codes do not set timing. Answer C is incorrect. Timing codes are not programmed. Answer D is incorrect. The cam follower is not adjusted.

157. An ether injector is shown in the figure. Technician A says that this device is used in conjunction with glow plugs as a cold weather starting aid. Technician B says that excessive use of this device can result in broken piston rings and ring lands. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C11)

Question #157 Answer B is correct. Only Technician B is correct. Excessive use of ether may result in broken piston rings and damaged piston ring lands. The automatic ether injection system is an optional starting aid. It is designed to spray a controlled flow of starting fluid into the air intake system during engine cranking in cold weather. Do not keep the starter engaged for more than 15 seconds at a time, and wait at least 30 seconds before trying again. With the automatic ether injection system, the engine should start in approximately 6 seconds, so cranking time should be kept short. If the engine will not start after several short cold cranking cycles, the other delivery system and its components should be checked. If the problem is not with the ether delivery system, the "no start" condition should be diagnosed to avoid over injecting the engine with ether. Answer A is incorrect. Ether should never be used with glow plugs. Vehicles equipped with glow plugs have warning labels warning against severe damage if ether is used. Answer C is incorrect, Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

158. Referencing the figure, Technician A says that a turbocharger assembly should never be disassembled because it is impossible to reassemble without expensive balancing instruments. Technician B says that turbochargers are often recorded by replacing the center housing as a unit and reusing the old compressor and turbine housings. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (E2)

Question #158 Answer B is correct. Only Technician B is correct. It is not uncommon practice to recore a turbocharger by replacing the center housing which is a pre balanced assembly. Recoring can only be performed if both the turbine and impeller housings are in good condition. Answer A is incorrect. Turbochargers are disassembled in the field. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

159. Technician A says wet cylinder sleeves should be cleaned by solvent immersion or with glass-bead blasting to the exterior. Technician B says a cylinder out-of-round condition can be detected by measuring at several locations with a dial bore gauge. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C4)

Question #159 Answer C is correct. Both Technicians A and B are correct. Technician A's method of cleaning a wet liner is a good one. Technician B is also correct in describing how to check for a cylinder out-of-round condition. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

16. During a check of the cooling system on a transit bus, a technician finds the system will not maintain pressure. No coolant leaks are visible anywhere on the vehicle. Technician A says the pressure relief valve may be stuck closed. Technician B says the engine must be running when pressurizing the cooling system. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D15)

Question #16 Answer D is correct. Neither Tech is correct. If the pressure relief valve were stuck closed, pressure would build, possibly to dangerous levels. When pressure testing a cooling system, it makes no difference whether the engine is running or not. Answer A is incorrect. Tech A is incorrect. The relief valve would have to be stuck open for the system to not maintain pressure. Answer B is incorrect. Tech B is incorrect. The engine does not have to be running to pressurize the cooling system. Answer C is incorrect. Neither Tech is correct

160. The figure shows what part of the lubrication system? A. oil filter B. oil cooler C. filter housing D. oil pump (D4)

Question #160 Answer B is correct. Oil coolers are heat exchangers consisting of a housing and a bundle (element/core) through which oil is pumped and around which coolant is circulated. Oil temperatures in diesel engines run higher than coolant temperatures, typically around 110°C (230°F). However, the engine coolant reaches its operating temperature more rapidly than the oil and plays a role in heating the oil to operating temperature in cold weather startup/warmup conditions. The figure shows an oil cooler bundle viewed from the header end. Answer A is incorrect. This is not an oil filter. Answer C is incorrect. This is not filter housing. Answer D is incorrect. This is not an oil pump.

161. Technician A says that mechanical rotators on a valve spring will help eliminate carbon deposits on the valve seat. Technician B says that they an prevent oil leakage from the valve guide. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B4)

Question #161 Answer A is correct. Only Technician A is correct. Valve rotators are used on diesel engine valves primarily to prevent carbon build-up on the valve seats. Answer B is incorrect. Valve rotators do not in any way help seal the valve guide. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

162. A vehicle has a turbocharger with a seized shaft bearing. Technician A says this could be caused by excessive engine idle time. Technician B says the oil supply line to the turbocharger should be replaced. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D5)

Question #162 Answer D is correct. Neither technician is correct. Answer A is incorrect. Technician A is incorrect, At idle speeds, the turbocharger is spinning at its slowest, and bearing load is light. As long as the turbocharger is receiving adequate lubrication, the amount of idle time should not be causing bearing damage. Answer B is incorrect. Technician B is incorrect. While a blocked oil supply line can cause oil starvation and bearing failure, the oil line to the turbocharger should be inspected to determine if replacement is necessary. Replacing parts without checking for failure first is poor practice. Answer C is incorrect. Neither technician is correct.

163. Technician A says that a starter solenoid has two coils. Technician B says that the hold-in coil draws more current than the pull-in coil. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (G6)

Question #163 Answer A is correct. Only Technician A is correct. A starter solenoid has two sets of windings or coils, the pull-in and hold-in windings. Answer B is incorrect. The pull-in winding draws more current than the hold-in winding, simply because it takes more force to pull the starter pinion into the engaged position than it does to hold it in the engaged position. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

164. Technician A says small coolant leaks can easily be detected, because antifreeze does not readily evaporate. Technician B says a defective thermostat can be caused by repeated overheating of the engine. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A2)

Question #164 Answer C is correct. Both Technicians A and B are correct. Technician A is correct because antifreeze does not readily evaporate, making it somewhat easy to detect small leaks. Technician B is also correct because repeated engine overheating can shorten the life of a thermostat. Cooling system leakage is common, and the system should be inspected by the operator daily. Cold leaks may be caused by contraction of mated components at joints, especially hose clamps. Cold leaks often cease to leak at operating temperatures. Many fleet operators replace all the coolant after a prescribed in-service period regardless of its appearance to avoid the costs incurred in a breakdown. Silicone hoses are more expensive than the rubber compound type but they usually have longer service life. Silicone hoses require the use of special clamps, and these are sensitive to overtightening. They must be torqued to the required specification. Pressure testing a cooling system will locate most external cooling system leaks. A typical cooling system pressure testing kit consists of a hand-actuated pump and gauge assembly calibrated to 625 psi (170 kPa) plus various adapters for the different types of fill necks and radiator caps. Some are capable of vacuum testing. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

165. A driver complains that a low coolant level alert is intermittently displayed. Technician A says this could be because coolant level in the radiator is low enough so that when the vehicle travels hilly terrain, the coolant level sensor ground is intermittently lost. Technician B says that this condition is normal even if the coolant level is correct, because any sloshing of the coolant in the radiator can trip the low coolant level alert. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.1)

Question #165 Answer A is correct. Only Technician A is correct. Depending on the location of the coolant level sensor, the coolant level may drop below sensor, triggering the fault. Once the coolant in the reservoir levels out, the fault will become inactive. Answer B is incorrect. Low coolant level alerts are time lagged in that no displayed warning is produced by the ECM until a specific time period has lapsed: 8 seconds would be typical. Currently, most electronically managed engines have radiators equipped with low coolant level warning systems. Most operate using the same principles. The ECM outputs a signal to a probe (or sensor), which grounds through the coolant. The probe is usually located in the top radiator tank. When the probe fails to ground through the coolant, a low coolant level warning is generated. The outcome depends on how the ECM has been programmed (this is a customer data program option). In most cases, a lag (from 5 to 12 seconds) is required before the ECM resorts to a programmed failure strategy, which may be to alert the operator, ramp down to a default rpm/engine load, or shut down the engine after a suitable warning period. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

166. On a vehicle with an electrical oil pressure gauge all of the following will cause inaccurate readings EXCEPT: A. low voltage to the gauge B. a short in the wire from the transducer C. low oil pressure D. a defective transducer (D1)

Question #166 Answer C is correct. Low voltage, a short in the wiring to the transducer, and a defective transducer will all cause inaccurate readings in an electric oil pressure gauge. However, low oil pressure in itself would not cause an inaccurate reading at the gauge. Of all the engine monitoring devices used on an engine, the oil pressure sensor is one of the most critical. Loss of engine oil pressure in most cases will cause a nearly immediate engine failure. Years ago when few of an engine's operating conditions were monitored and displayed to the operator, there was always a means of signaling a loss of oil pressure. Several types of sensors are used in today's engines, including: variable capacitance (pressure) sensor, piezoelectric, bourdon gauge, and an electrical gauge. Whichever is used to display oil pressure, none should be used as the only means of diagnosing low oil pressure. Use a good quality master gauge such as a gauge with a fluid-filled display dial. CAUTION: When disconnecting high-pressure oil lines on HEUI high- pressure oil pumps, relieve the system pressure first; wear safety glasses when performing this procedure to avoid personal injury. Answer A is incorrect. Low voltage would cause the gauge to read inaccurate. Answer B is incorrect. A short in the transducer would cause the gauge to read incorrectly. Answer D is incorrect. A defective transducer would cause the gauge to read incorrectly.

167. A recently overhauled engine develops cylinder hydraulic lock. After clearing the liquid from the cylinder, inspecting the heads, and replacing the head gaskets the problem reoccurs. Technician A says the intercooler could be defective, Technician B says the cylinder head may have a hairline crack. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B3)

Question #167 Answer C is correct. Both Technicians A and B are correct. Cylinder hydraulic lock is usually caused by liquid (generally engine coolant) filling the cylinder above the piston, preventing the engine from rotating. Both the intercooler (such as would be used on a DDC 2-stroke cycle engine) and a crack in a cylinder head are possible sources of coolant that fills a cylinder. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

168. What would the technician do fist when adjusting dive belts on an engine? A. replace the drive pulleys B. replace the idler pulleys C. check belts for cracking and wear D. apply belt dressing compound (D7)

Question #168 Answer C is correct. The first step is to check the belts for cracking and wear. If worn or there is evidence of cracks, the belts should be changed, not adjusted. Fan pulleys use external V or poly-V grooves and internal bearings of the roller, taper roller, and bushing types. The belt tension should be adjusted using a belt tensioner. Answer A is incorrect. Drive pulleys are not replaced just because the belts are being adjusted. Answer B is incorrect. Idler pulleys are not replaced just because the belts are being adjusted. Answer D is incorrect. Belt dressing compound is not typically approved by OEMS.

169. A vehicle is reported to have poor fuel mileage. Tech A says that missing thermostats could be the cause. Tech B says a leaking fuel line could be the cause. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D9)

Question #169 Answer C is correct. Both Technicians A and B are correct. Thermo stats allow the engine to reach and maintain operating temperature. If thermostats were not installed, the coolant would continuously circulate through the radiator and never reach proper operating temperature. Diesel engines tend to waste fuel at lower temperatures due to incomplete combustion. Operating the engine below normal temperature will cause increased fuel consumption. If the fuel line were leaking, fuel would be wasted and cause fuel mileage to decrease. Both technicians are correct. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

17. A small crack is detected in a wet sleeve around the counterbore flange. Technician A says to use helia-arc welding to seal the crack. Technician B says the block needs to have the counterbore recut. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C4)

Question #17 Answer D is correct. Neither technician is correct. Answer A is incorrect. A crack in the counterbore flange of a wet sleeve is reason to replace it, So Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. It is possible the wet sleeve flange has cracked and produced no damage to the block counterbore. The block counterbore should be carefully measured and inspected. Answer C is incorrect. Neither technician is correct.

170. When installing the starter, which is LEAST-Likcly to be done? A. Connect control wiring to solenoid B. align starter motor with flywheel C. install starter mounting bolts D. replace starter bushings (G8)

Question #170 Answer D is correct. Replacing the bushings is part of starter motor overhaul, not part of installing it. Answer A is incorrect. Control wiring would be reinstalled. Answer B is incorrect. The motor would be aligned. Answer C is incorrect. The mounting bolts must be reinstalled.

171. A set of dry liners are to be fitted to a diesel engine cylinder block. Technician A says that it is good practice to selectively fit the liners to block by fitting the liner with the largest OD o the block bore with the largest ID and progressing downward. Technician B says that it is important to machine the correct crosshatch pattern into the block bore before fitting each liner. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C3)

Question #171 Answer A is correct. Only Technician A correctly descríbes the recommended practice process of selectively fitting a set of dry liners to a cylinder block. Answer B is incorrect. Crosshatch is not required to be cut to the cylinder block bore in any engine that uses liners; this is machined to the liner bore. The dry liner uses thinner-walled sleeves than the wet liner. Dry liners (sleeves) are installed into the block bore, usually with a marginally loose fit, and are retained by the cylinder head. The dry sleeves do not transfer heat as efficiently as the wet liners, but they are easily replaced and do not present coolant-sealing problems. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

172. What is the function of the component in the figure? A. fuel transfer pump B. coolant pump C. fuel injection pump D. oil pump (D3)

Question #172 Answer D is correct. The figure shows a gear-type engine oil pump and pressure relief valve assembly. Gerotor-type oil pumps use an internal crescent gear pumping principle. An internal impeller with external crescent vanes is rotated within an internal crescent gear, also known as a rotor ring. The inner rotor or impeller has one less lobe than the rotor ring. As the inner rotor is driven within the outer rotor, only one lobe is engaged at any given moment of operation. In this way, oil from the inlet port is picked up in the crescent formed between two lobes on the impeller. As the impeller rotates, oil is forced through the outlet port as the lead lobe once again engages. The assembly is rotated within the Gerotor pump body. Answer A is incorrect. This is not a fuel transfer pump. Answer B is incorrect. This is not the water pump. Answer C is incorrect. This is not the fuel injection pump.

173. Upon inspection of the engine compartment, the engine and most of the engine compartment is covered with a thin layer of black soot. Which of these is the most likely cause? A. Excessive idling B. a malfunctioning boost pressure sensor. C. a cracked exhaust manifold D. loose air intake hose clamps (E5)

Question #173 Answer C is correct. Diesel exhaust normally contains small amounts of soot and ash. Black sooty deposits in and around the engine compartment are telltale signs of exhaust system leaks. A is incorrect. Excessive idling will not cause soot build-up inside the engine compartment. B is incorrect. Although a malfunctioning boost pressure sensor can cause overfueling and excess soot, the soot would normally exit through the tailpipe and not collect in the engine compartment. Answer D is incorrect. Loose air intake hose clamps would allow dirt to enter the intake air stream, not produce soot deposits.

174. Low engine power has been determined to be a result of insufficient fuel delivery to the unit injectors. Which of the following would be the LEAST-Likely cause? A. suction circuit leaks in fuel subsystem B. defective fuel transfer pump C. clogged fuel filter D. a leak in the injector return line (A12)

Question #174 Answer D is correct. Suction circuit leaks, improperly set throttle lever angle, and clogged fuel filters can all result in a low power condition. However, a leak in the injector return circuit is unlikely to cause low power, so it is the LEAST-Likely cause of the problem. Answer A is incorrect. Suction circuit leaks cause low power. Answer B is incorrect. A defective fuel transfer pump will cause low power. Answer C is incorrect. A clogged fuel filter will cause low power,

175. After wet-type cylinder sleeves have been removed, the packing ring area and counterbore show signs of light rust and scale. Tech A says this is normal and no additional action is required except ensuring antifreeze protection includes rust inhibitors. Tech B says to use 100- to 120-grit emery paper to remove rust and scale, and check for erosion and pitting. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C2)

Question #175 Answer B is correct. Only Technician B is correct. Indications of corrosion in any sealing surface of a wet liner must be addressed or the liner will leak when installed. Answer A is incorrect. If the rust and scale are not removed, the liner O-rings will most likely leak. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

176. Which component of a mechanical unit injector (MUI) system is LEAST-Likely to be the cause of an improper injector spray pattern? A. nozzle-tip holes B. injection nozzle valve C. injector rack D. injector follower (F1.7)

Question #176 Answer C is correct. The MUI rack controls the plunger effective stroke so it will not cause a spray pattern problem. Answer A is incorrect. Nozzle-tip holes can cause an improper spray pattern. Answer B is incorrect. The injection nozzle valve can cause improper spray patterns. Answer D is incorrect. A worn injector follower can cause no spray from the injector.

177. Which tool is Most-Likely to be used to determine the starter circuit voltage drop test? A. starter shunt resistor B. voltmeter C. ohmmeter D. millimeter (G8)

Question #177 Answer B is correct. Voltage drops test resistance in an energized circuit, and as such they are the most meaningful method of checking active circuits. Only a voltmeter can be used to perform this test. Getting used to using your DMM on real-world circuits means testing properly functioning circuits. Too often, a technician tests a circuit for a defect without knowing how the circuit would test if it was fully functional. Make a practice of testing good circuits as well as bad. Remember, your DMM is capable of making exact measurements and the specific value is Significant. When evaluating circuit performance, there is a difference between 12.6 and 12.5 volts; make a habit of writing down the results of circuit testing. Answer A is incorrect. A shunt resistor would not be used. Answer C is incorrect. An ohmmeter cannot measure voltage. Answer D is incorrect. A millimeter is a distance measurement.

178. Which of the following is LEAST-Likely to provide satisfactory results when attemptıng to identify an engine miss? A. Listening to the exhaust to determine which cylinder is misfiring B. Using a stethoscope C. Manually shorting out each hydromechanical injector D. Performing an electronic cylinder cut-out test on computer-controlled engines. (A4)

Question #178 Answer A is correct. Using a stethoscope, shorting out hydro mechanical injectors, and performing an electronic cylinder cut-out test are all valid procedures when attempting to troubleshoot an engine miss. However, attempting to locate an engine miss by listening to the exhaust is unlikely to locate which cylinder is misfiring so this is the LEAST-Likely to produce satisfactory results. Answer B is incorrect. Using a stethoscope is a valid method of identifying an engine miss. Answer C is incorrect. Manual shorting out (depressing) a hydromechanical injector is a good test method. Answer D is incorrect. An electronic cut-out test is a valid test method.

179. Which procedure is LEAST-Likely to be used when performing valve seat maintenance? A. testing seats for looseness with a ball-peen hammer B. using a chisel to remove defective seats C. checking seats with a concentricity indicator D. dressing a valve seat grinding stone (B4)

Question #179 Answer B is correct. Using a chisel to remove valve seats is not good practice because the cylinder head can be damaged; the rest of the answers reference appropriate steps when performing cylinder valve service. Most current truck diesel engines use valve seat inserts rather than integral valve seats machined into the cylinder head. Valve seat inserts are press-fit to a machined recess in the cylinder head. Since most of the heat of the valve must be transferred from the valve to the seat, it is essential that the contact area of the seat and the cylinder head be maximized. A sectored collet that expands into the valve seat is used to remove the valve seat. The seat can either be levered out or driven out with a slide hammer. When installing new valve seats, the seat counterbore must be first cleaned out using a low-abrasive emery cloth. Answer A is incorrect. A valve seat can be struck lightly with the ball-peen end of a hammer. If the seat "rings" it is loose. Answer C is incorrect. Valve seats are checked for concentricity with the guide. Answer D is incorrect. Valve grinding stones should be dressed prior to being used.

18. An electronically managed diesel engine produces white smoke on cold startup for at least 10 minutes. Technician A says this is normal and, providing the exhaust smoke cleans up once the engine is at running temperature, nothing should be done. Technician B says that there could be a problem with the cold-start strategy and the engine should be immediately checked. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A5)

Question #18 Answer B is correct. Only Technician B is correct. All current electronically managed engines have programmed cold-start strategies that limit engine smoking during start and warmup. Answer A is incorrect. An engine that produces white smoke for 10 minutes after startup is not functioning properly. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

180. When air-pressure testing an engine block, Technician A says the block need only submerged in hot water for about 20-30 minutes and the water checked for bubbles. Technician B says cracked cylinder blocks should be replaced. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C2)

Question #180 Answer C is correct. Both Technicians A and B are correct. When pressure testing a cylinder block for suspected cracks, immersing it in hot water for 2030 minutes should be sufficient to swell any cracks to observe a leak. Most diesel engine manufacturers recommend that a cracked cylinder block be replaced rather than repaired. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

181. The figure shows which of the following valve conditions? A. eroded valve stem B. carbon deposits on valve face C. ridging on valve face D. stretched valve stem (B4)

Question #181 Answer D is correct. The figure shows a valve stem stretched at the fillet. Answer A is incorrect. The figure shows a valve stem stretched at the fillet. Answer B is incorrect. The figure shows a valve stem stretched at the fillet. Answer C is incorrect. The figure shows a valve stem stretched at the fillet.

182. For what task is the tool in the figure designed to perform? A. remove the Iiner carbon ridge B. remove the cylinder liner C. machine the liner crosshatch pattern D. cut the liner counterbore (C3)

Question #182 Answer D is correct. The tool shown is designed to cut a cylinder liner counterbore. Check the cylinder sleeve counterbore for the correct depth and circumference. Counterbore depth should typically not vary by more than 0.001 in. Counterbore depth can be subtracted from the sleeve flange dimension to calculate sleeve protrusion. Recut and shim the counterbore using OEM- recommended tools and specifications. Answer A is incorrect. This is not a ridge remover. Answer B is incorrect. This is not a liner remover. Answer C is incorrect. This machine does not machine the crosshatch.

183. A vehicle is being checked for an inoperative exhaust brake. Tech A says the vehicle's air system pressure should be checked. Tech B says the actuator valve return spring may be broken. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (E8)

Question #183 Answer A is correct. Only Technician A is correct. Most exhaust brakes are actuated using compressed air supplied by the vehicle's air system. If system pressure to the actuator is insufficient to close the valve, the brake will not work. Technician A is correct in checking that the proper amount of air is available. Answer B is incorrect. If the valve's return spring was broken, the brake would apply, but it would most likely not release. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

184. When performing failure analysis on a trunk-type piston, heavy erosion and pitting is evident just above the NI-resist insert on the upper compression ring. Tech A says this is probably caused by fuel with low CN rating. Tech B says that the cause is advanced fuel injection timing. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C14)

Question #184 Answer B is correct. Only Technician B is correct. Advanced fuel injection timing damages the outer edges of the piston and melts, eroding the top ring land above the Ni-resist insert. The erosion is caused by fuel dispersal/condensation outside of the combustion bowl. Answer A is incorrect. Fuel with low CN is likely to produce failures consistent with retarded timing. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect, Only Technician B is correct.

185. Tech A says that when removing high-pressure fuel lines, the seat nipples must be capped to keep out contaminants. Tech B says that overtorquing high pressure line nuts can cause restricted fuel flow. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F1.10)

Question #185 Answer C is correct. Both Technicians A and B are correct. When high-pressure fuel injection lines are removed from an engine, it is essential to immediately cap them to prevent the entry of dirt and dust. Technician A is correct. Low power in PLN fuel systems can be caused by over torquing of high-pressure line nuts, which collapses the sealing nipple, reducing flow potential. So Technician B is also correct. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

198. When replacing the electronic control module (ECM) on an engine with electronic unit injectors (EUIS), what must the technician do first? A. disconnect the battery B. download customer data C. remove injector lines D. Turn on the key (F2.4)

Question #186 Answer B is correct. Only Technician B is correct. Fuel to be injected is metered by the rail actuator solenoid. Fuel is directed into and out of the HPI-TP injectors by means of 3 exterior annuli separated by 4 O-ring seals. The upper annulus feeds timing fuel to the injector, the middle annulus discharges drain/spill fuel, and the lower annulus receives the metering fuel. Answer A is incorrect. The diagram shows an HPI-TP injector. The fuel passing through the timing orifice acts as a hydraulic slug to define timing and none of it will be injected; it is routed back to the fuel tank. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct

197. Which of the following would more likely result from excessive ether usage during cold startup? A. engine runaway B. cylinder hydraulic lock C. fuel injection system damage D. damaged piston compression ring lands (C11)

Question #187 Answer C is correct. Both Technicians A and B are correct. Technician A correctly describes how to remove the surface charge from a battery that has been recently charged. Also, a stored battery does not have a surface charge. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

186. Referencing the figure, Technician A says that all of the fuel passing through the timing orifice is injected to the engine during the fuel pulse. Technician B says that fuel to be injected is metered by the rail actuator solenoid. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.4)

Question #188 Answer C is correct. Both technicians are correct. By-pass or centrifugal oil filters should be serviced at the same interval as the oil and full-flow filters are changed. This will ensure the centrifuge is operating at peak efficiency. A full bowl or sudden increase in the amount of material collected in the centrifuge bowl can indicate excessive contaminants entering the engine oil. This can be caused by cracked or worn piston rings, excessive blow-by, or poor air filtration. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

196. What is the technician measuring in the figure? A. cam lobe B. cam bearing journal diameter C. cam lift D. cam duration

Question #189 Answer D is correct. All of the checks are valid EXCEPT for the one referencing the interference fit of the liner into the cylinder bore. Wet sleeves are never interference fitted to the cylinder block bore; they are sealed with O-rings. Dry sleeves are interference fit. Answer A is incorrect. The contact surfaces should be inspected. Answer B is incorrect. The O-ring grooves should be inspected. Answer C is incorrect. The bore should be inspected for scoring.

19. Camshaft bearing diameter should be measured with a A. feeler gauge. B. inside micrometer. C. Plastigage. D. Manometer. (C6)

Question #19 Answer B is correct. When determining if camshaft bearings are suitable for reuse, the inside diameter should be checked against the manufacturer's specifications for wear. The correct tool for this measurement is an inside micrometer. Answer A is incorrect. A feeler gauge is used to measure clearance between parts. Answer C is incorrect. Plastigage is used to measure clearance between parts. Answer D is incorrect. A manometer 1S used to measure pressure.

187. Technician A says to remove the surface charge from a recently charged battery, apply a 300-mpere load across the terminals for 15 seconds. Technician B says that it is unnecessary to remove the surface charge from batteries which have been in storage. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (G1)

Question #190 Answer B is correct. Only Technician B is correct. The pump shown in the center of the V cradle in this figure is the HEUI high-pressure oil pump that pressurizes engine oil to actuate the HEUI injectors. If this pump is producing lower than specified pressure, one of the results would be low power. Answer A is incorrect. The pump does not supply fuel to the injectors. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

195. A vehicle equipped with electronically controlled diesel engine has the stop engine light (SEL) illuminated, but not flashing. Technician A says that this indicates the idle shutdown timer has timed out and the engine will shutdown within 60 seconds. Technician B says that the ECM bas detected a problem that could result in serious engine damage and, if programmed to, may shutdown the engine. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.5)

Question #191 Answer B is correct. Only Technician B is correct. Crankcase pressure should be tested across a range of rpms and engine loads usually under monitored test conditions such as would be found on a dynamometer. The highest crankcase pressures are produced when engine cylinder pressures are high and engine speeds are low (more time for cylinder blowby each cycle). Answer A is incorrect. The engine is normally run at varying rpms. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

188. Technician A says the centrifugal oil filter should be serviced at the same time as a regular oil change interval. Technician B says a completely full centrifuge bowl can indicate a severe engine problem. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D6)

Question #192 Answer A is correct. Only Technician A is correct. When boosting a vehicle using another, it is good practice to switch off the engine of the boost vehicle while making the battery connections to prevent electrical/electronic damage. Answer B is incorrect. Most bus electronically managed engines are designed to sustain transient (short-term) voltage overloads such as would be caused by a portable generator, a common start assist tool. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

194. Multiple fractures are discovered in a crankshaft. Technician A says the failure analysis must include inspection of the vibration damper. Technician B says the flywheel should also be closely inspected. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C8)

Question #193 Answer C is correct. Both Technicians A and B are correct. Jacket water aftercoolers (JWAC) use a split design intake manifold that contains the aftercooler core. The water pump pumps engine coolant through the aftercooler core. Incoming air moving from the compressor side of the turbocharger through the intake manifold is at approximately 300°F (148°C) before going through the aftercooler core. This action reduces the air temperature to approximately 195°F (91°C), thereby increasing its density. Both air locked in the intercooler and clogged air tubes could cause lack of power and higher coolant temperatures. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

189. When installing a wet cylinder sleeve all of the following should be checked EXCEPT: A. contact surfaces between the sleeve and the cylinder block B. O-ring grooves C. bore of the sleeve for Scoring D. interference fit between the sleeve and block bore (C5)

Question #194 Answer C is correct. Technicians A and B are correct. When a crankshaft fails, especially if the indications are that it is a torsional failure, everything on its powertrain (driven by it) should be closely inspected. Both technicians are correct because the vibration damper and flywheel are among the first components that should be inspected. Torsional stresses are the twisting vibrations that a crank is subjected to at high speed. Crankshaft torsional vibration occurs because while under compression (that is, driving the piston assembly attached to it upward on the compression stroke) a given crank throw wll slow to a speed marginally less than average crank speed. Subsequently, when the throw receives a power stroke, it will accelerate to a speed marginally greater than average crank speed. These twisting vibrations or oscillations take place at high frequencies, and crankshaft design, materials, and hardening methods must take them into account. Torsional stresses tend to peak at crank journal oil holes at the flywheel end of the shaft. Torsional oscillations are amplified when an engine is run at slower speeds with high cylinder pressures, because the real-time duration between cylinder firing pulses is extended. This type of running (lower speed/high load) is known as lugging, but with many new generation, high torque-rise engines, engine torsional oscillations can be projected through the drivetrain. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect, Both technicians are correct.

193. Reduced power and high coolant temperature are observed on an engine with an intercooler, as shown in the figure. Technician A says there may be an air lock in the coolant, and it is necessary to bleed air out of the intercooler. Technician B says the air tubes in the cooler may be clogged. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (E4)

Question #195 Answer B is correct. Only Technician B is correct. The system has two warning lights. The check engine light signals a fault or intermittent fault to the driver. The stop engine light, which illuminates when the ECM has detected a problem that could result in serious engine failure, may be programmed to shut down the engine or ramp down to idle after the ECM detects a problem. Answer A is incorrect. A flashing SEL light would indicate that the idle shutdown timer had timed out. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

190. The electronically controlled HEUI fuel system shown in the figure has a low power complaint. Technician A says that the pump shown is supplying fuel to the injectors. Technician B says that low actuation oil pressure could be the cause. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.3)

Question #196 Answer B is correct. The cam bearing journal diameter is being measured. Answer A is incorrect. The cam lobe is not being measured. Answer C is incorrect. Cam lift is not being measured. Answer D is incorrect. Cam duration is not being measured.

192. A vehicle with a standard 12-V charging/cranking circuit has to be boost started. Technician A says that the battery-to-battery connections should be made with the boost vehicle engine switched off. Technician B says that a portable generator (blast charger) cannot be used on electronically managed engines because high voltage can destroy the engine ECM. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (G4)

Question #197 Answer D is correct. Excessive use of ether to start an engine causes much higher cylinder pressures that can blow out piston ring lands. Answer A is incorrect. Ether is unlikely to be the cause of an engine runaway because it ignites early and combusts very rapidly. Answer B is incorrect. Ether will cause vapor lock, not hydraulic lock. Answer C is incorrect. Ether will not damage the fuel system; ether is introduced into the air system.

191. Technician A says that to test an engine for excess crankcase pressure the engine must be run at low idle. Technician B says the engine must be tested across a range of operating speeds and loads. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A10)

Question #198 Answer B is correct. When the diagnostics determine that the ECM has to be changed, the customer data programming should be downloaded (and printed off if required) so this can be loaded onto the replacement ECM. Answer A is incorrect. The battery should be disconnected during ECM replacement, however, the customer data should be downloaded first. Answer C is incorrect. Injection lines do not need to be removed to replace the ECM. Answer D is incorrect. The key should be off during ECM replacement.

2. When performing voltage drop tests on the starting circuit in the figure, what should be the normal voltage drop across the solenoid switch contacts? A. 3.0 volts B. More than 9.6 volts C. Less than 0.01 volts D. 0.3 volts (G8)

Question #2 Answer D is correct. Voltage dropped overcoming resistance at the solenoid switch contact should be as low as possible, about 0.3 volts, leaving the majority of available voltage for the starter motor. Answer A is incorrect. This would be eXcessive voltage drop. Answer B is incorrect. This would be excessive voltage drop. Answer C is incorrect. The choice of 0.01 volts is so low that it is unlikely to even be possible.

20. Technician A says that only manufacturer software is compatible with diagnostic data bus protocols. Technician B says that each manufacturer uses a different data link connector, so only their diagnostic instruments can be used. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.1)

Question #20 Answer D is correct. Neither technician is correct. Vehicle engine and chassis manufacturers adhere to SAE J1587/1708 and J1939 hardware and communications protocols to provide common access to electronic readouts and diagnostic codes by any instrumentation that is SAE compatible. All vehicle manufacturers use either a 6- or 9-pin ATA connector. Multiplexing standardization for vehicles has been orchestrated by ISO (International Organization for Standardization) internationally and by the SAE (Society of Automotive Engineers) in North America. In North America, SAE J standards, J1850 (light-duty vehicles), and J1939 (heavy-duty highway vehicles) define the hardware and software protocols of multiplexed components and data transfer. ISO CAN 2.0 is consistent with J1850 and J1939 standards used in the United States and Canada. The SAE J1939 combines and replaces the older J1587/1708 hardware and software protocols. Current vehicles tend to be both J1939 and J1587/1708 compatible. Answer A is incorrect. Tech A is incorrect Answer B is incorrect. Technician B is incorrect. Answer D is incorrect. Neither technician is correct.

21. All of the following would be used while performing an alternator amperage output test EXCEPT: A. a carbon pile load tester B. amp clamp C. refractometer D. voltmeter (G7)

Question #21 Answer C is correct. To perform an alternator amperage output test, an amp clamp is placed around the wire attached to the alternator's output terminal, engine rpm is increased to high idle. and a load is gradually placed across the battery terminals with a carbon pile load tester until maximum amperage output is reached without reducing battery voltage below 12 volts. A refractometer is used to test specific gravity. Answer A is incorrect. A carbon pile tester is used to create a load on the alternator. Answer B is incorrect. An amp clamp can be used to measure alternator output. Answer D is incorrect. A voltmeter is used to measure alternator voltage.

22. Technician A says before installation, head bolts must be cleaned and inspected for erosion or pitting. Technician B says the cylinder deck needs to be checked for warpage before installing the head. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B2)

Question #22 Answer C is correct. Both Technicians A and B are correct. It is important to check cylinder head bolts prior to installing them into the cylinder head, so Technician A is correct. Technician B is also correct. The cylinder block deck must be checked for warpage before installing the head. Readings beyond this specification indicate the need to resurface the block fire deck. However, you should always refer to the OEM service manual for the correct value. Blocks do not warp nearly as often as cylinder heads. When the block fire deck is warped or not parallel to the main bearing bores, it may be resurfaced with a milling machine or grinder. Next, check the main bearing bore and alignment. It is good shop practice to record the amount of stock removed from the deck by stamping the amount removed on the cylinder block pad. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

23. Technician A says that it is permitted to mix ethylene glycol (EG) and propylene glycol (PG) antifreeze in a cooling system but that the mixture concentration can only be tested using a refractometer. Technician B says that extended life coolant mixture should never have water added to it. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D10)

Question #23 Answer B is correct. Only Technician B is correct, ELC should only have premix added, never water. Ethylene glycol is derived from ethylene oxide, which is produced from ethylene, a basic petroleum fraction. Propylene glycol is derived from propylene oxide, which is produced from propylene, another basic petroleum fraction. When mixed in a solution with water, both PG and EG are described as aqueous. Answer A is incorrect. Propylene glycol- and ethylene glycol-based coolants should never be mixed. The mixture itself will not cause any engine or cooling system problems, but it will be impossible to determine the antifreeze mixture strength with either a refractometer or a hydrometer. If a mixture of EG and PG is known to have taken place and the coolant cannot be immediately replaced, use a refractometer with an EG and a PG scale, and average the two readings. However, the cooling system should be drained and refilled with either aqueous PG or EG when practical to avoid problems later on. ELC is only sold premixed and is dyed a red color. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

24. Which of the following would be Most-Likely to cause a fuel starvation problem to shut down an engine? A. plugged fuel tank breather B. intake manifold leak C. insufficient throttle an travel D. missing fuel tank cap (A2)

Question #24 Answer A is correct. A plugged fuel tank breather can create a below-atmospheric pressure in the fuel tank that the fuel transfer pump is unable to overcome, resulting in engine shutdown due to fuel starvation. Currently, most jurisdictions in North America permit venting of diesel fuel tanks to the atmosphere. Therefore, as fuel is pumped out of on-board tanks. it is replaced by ambient air drawn in through vent valves. Answer B is incorrect. A leaking intake manifold would result in a high whistling sound and possible dirt ingestion in the engine; however, it would not starve for fuel Answer C is incorrect. Insufficient throttle travel would cause low power, but not fuel starvation Answer D is incorrect. A missing fuel tank cap would cause contaminated fuel, but would not directly cause fuel starvation

25. Technician A says most oil pump pressure-regulating valves are factory-sealed devices. Technician B says if an oil pump pressure-regulating valve fails, the oil pump must be replaced. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D3)

Question #25 Answer D is correct. Neither technician is correct. Oil pump regulating valves are responsible for defining the maximum system oil pressure; most are adjustable, typically, an oil pressure-regulating valve consists of a valve body with an inlet sealed with a spring-loaded, ball-check valve. Other types of poppet valves are also used, but the principle is the same. The regulating valve body is plumbed in parallel to the main oil pump discharge line. When oil pressure is sufficient to unseat the spring-loaded check ball, it unseals, permitting oil to pass through the valve and spill to the oil sump. This action will cause the pressure in the oil pump discharge line to drop. Answer A is incorrect. Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. Answer C is incorrect. Neither technician is correct.

26. Technician A says the tool as shown in the figure is used to bore out cylinder liners. Technician B says it is to check liner protrusion. Who is correct? A. A only B. B only C. Both A and B D, Neither A nor B (C5)

Question #26 Answer D is correct. Neither technician is correct. Sleeves should be removed with a puller and adapter plate or shoe. The procedure is obviously more simple on wet liners. The tool shown is a liner puller. Answer A is incorrect. Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. Answer C is incorrect. Neither technician is correct.

27. Technician A says that most engine management computers permit fault codes to read by flashing codes through dash diagnostic lights. Technician B says that digital driver displays (DDD) on the dash on many current vehicles will alert the operator to any conditions that could affect the operation of the vehicle. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.1)

Question #27 Answer Cis correct. Both Technicians A and B are correct. Most engine management computers are equipped with a means of displaying fault codes without the use of diagnostic instruments. This can be by means of flashing codes as an example. Most current vehicles also now have digital dash displays that alert the driver to any conditions that affect the operation of the vehicle. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

28 An engine being overhauled is found to have pistons with cracked skirts. Technician A says this could have been caused by excessive piston-l0-cylinder wall clearance. Technician B says this could have been caused by running the engine with a low oil level. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (CI2)

Question #28 Answer A is correct. Only Technician A is correct. One of the effects of too much clearance between the piston and the cylinder wall is piston rockıng. If the pistons are allowed to rock. they will stress the sides and crack the skirts. Piston-to-cylinder clearance should be kept to specification to allow the pistons to remain straight in the bore. Answer B is incorrect. Running the engine with a low oil level may cause piston and cylinder scuffing, but will not cause cracked skirts. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

29. Droplets of water or gray oil on the dipstick would LEAST-Likely be caused by a A. cracked block or cylinder head. B. blown head gasket. C. leaking oil cooler bundle. D. worm oil pump. (A2)

Question #29 Answer D is correct. Droplets of water or gray oil on a dipstick would LEAST-Likely be caused by a worn oil pump. All the other answers are indications that coolant has leaked into the oil. Coolant in the engine lubricant gives it a milky, cloudy appearance when churned into the oil. After settling, the coolant will usually collect at the bottom of the oil sump. When the drain plug is removed, the heavier coolant will exit first, as long as sufficient time has passed since running the engine. When coolant is found in the engine oil, the cylinder-head injector tubes and cylinder head gasket are the most likely sources. Answer A is incorrect. A cracked block or cylinder head could cause this condition. Answer B is incorrect. A blown head gasket could cause this condition. Answer C is incorrect. A leaking oil cooler bundle could cause this condition.

3. When performing failure analysis on a set of crankshaft main bearings, one is observed to be heat discolored on the backing (block) side. Which of the following would be Most-Likely to create this condition? A. excessive big endplay B. insufficient bearing crush C. belled crankshaft main journal D. degraded engine lube (C9)

Question #3 Answer B is correct. Friction-bearing shells must be able to dissipate the heat they are subjected to in the bore into which they are inserted. Bearing crush helps ensure good heat transfer by making it possible to transfer heat. When bearing crush is insufficient, there is less force loading the bearing into its bore and it does not transfer heat as efficiently. Dirt or grease on the back of the bearing would have the same effect. Bearings are retained primarily by crush. The outside diameter of a pair of uninstalled bearing shells slightly exceeds the bore to which it is installed. This creates radial pressure that acts against the bearing halves and provides good heat transfer. The bearing halves are also slightly elliptical to allow the bearing to be held in place during installation; this is known as bearing spread, Tangs in bearings are inserted into notches in the bearing bore to minimize longitudinal movement, prevent bearing rotation, and align oil holes. Answer A is incorrect. Excessive play would not cause the back of the bearing to be discolored. Answer C is incorrect. A belled crankshaft journal would establish a wear pattern on the bearing front, not back. Answer D is incorrect. Degraded lube would establish wear on the front of the bearing, not the back.

30. Technician A says that low manifold boost pressure can be caused by air inlet restriction. Technician B says that you can check turbo boost pressure with a water manometer. Who 1S correct? A. A only B. B only C. Both A and B D. Neither A nor B (A8)

Question #30 Answer A is correct. Only Technician A is correct. Low manifold boost can be caused by air inlet restriction so Technician A is correct. Answer B is incorrect. Manifold boost cannot be checked with a water manometer. Peak boost in truck diesel engines is typically 35 psi, which is equivalent to 970 inches of water in a manometer. Answer C is incorTect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

31. Technician A says valve rotators can be tested using a plastic mallet tapping the valve stems. Technician B says defective valve seals will cause oil consumption. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B4)

Question #31 Answer C is correct. Both Technicians A and B are correct. Valve rotators use a ratchet principal or a ball and coaxial spring to rotate the valve fractionally each time it is actuated. Valve rotation should be checked after assembly by marking an edge of the stem and then tapping the valve stem with a light nylon hammer a number of times. The valve should visibly rotate each time the stem is struck. Technician A's method of verifying whether valve rotators are rotating is good practice so he is correct. Technician B is also correct in saying that defective valve seals can cause oil consumption. Oil will leak past defective valve guide seals and into the combustion chamber. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

32. A vehicle is checked for poor acceleration. The engine idles normally, but is slow to generate boost pressure. Once the vehicle is at higher road speeds, the vehicle runs normally. Which could be the Most-Likely cause of this condition? A. an inoperative wastegate actuator B. a leaking intake manifold gasket C. a clogged air filter D. a plugged EGR port (E3)

Question #32 Answer B is correct. Small leaks in the intake manifold gasket will cause boost pressure to build very slowly, affecting acceleration. Once the vehicle speed has increased, boost pressure is much higher and the reduced boost level is less noticeable. At idle speeds, little to no boost is produced, so the leak will not affect engine operation at idle speeds. Answer A is incorrect. An inoperative wastegate actuator would have no affect on acceleration. The boost levels would be able to go higher than normal, possibly damaging air system components. Answer C is incorrect. A clogged air filter would cause engine performance problems through all speed ranges. Answer D is incorrect. A plugged EGR port would affect EGR System operation, but would have no affect on boost pressure.

33. To maintain an effective cooling system, all of the following must be done EXCEPT: A. The radiator and engine must be back-flushed annually. B. Coolant should be tested for SCA strength and acidity. C. Air must be bled from the engine during refilling of the system. D. Coolant should be tested for antifreeze protection level. (A14)

Question #33 Answer A is correct. All the steps listed are required to maintain effective cooling in a diesel engine EXCEPT flushing and refillıng of the cooling system annually. Some extended-life cooling systems are designed to last for up to five years and back-flushing is seldom recommended by diesel engine manufacturers. Answer B is incorrect. Coolant should be tested regularly. Answer C is incorrect. Air must be bleed from the cooling system during refilling to prevent engine damaging air pockets. Answer D is incorrect. Coolant must be tested for antifreeze protection level. This is usually done by test strips or a refractometer.

34. Technician A says that an easy way to erase fault codes on most diesel engine ECMS is to disconnect the vehicle batteries. Technician B says that when the vehicle batteries are disconnected. none of the tattletales and audit trails are lost because they are written to EEPROM. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (Al6)

Question #34 Answer B is correct. Only Technician B is correct. Fault codes in most diesel engine management systems are logged in EEPROM, So the act of disconnecting the vehicle batteries is not going to erase them. Answer A is incorrect. Most modern diesel engine ECMS write fault code information to the nonvolatile memory, which is not erased when power is removed. Usually the only way to erase fault codes is through the use of approved test equipment, so Technician A is incorrect. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

35. Technician A says that some ELC coolants require only one SCA treatment in six years. Technician B says that engine cooling fan engagement may be included in engine braking strategy. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A14)

Question #35 Answer C is correct. Both Technicians A and B are correct. Extended Life Coolants (ELC) are low-maintenance coolants that may require only one SCA treatment in six years. The engine-cooling fan may be engaged for engine braking as part of engine brake strategy. ELCS promise a service life of 600,000 miles (960,000 km) or six years, with one additive recharge at 300,000 miles (480,000 km) or three years. This compares with a typical service life of two years during which up to 20 recharges of SCA would be required for conventional EG and PGs. ELCS are presently available only as a premixed solution to ensure that the water quality is at the required level. The pricing of ELCS by quantity is generally comparable with EG and PG, but because of reduced cooling system maintenance and extended service life, they will probably become the coolant of choice of the engine OEMS. No test kits are required to monitor the ELC SCA level. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

36. You suspect a cylinder head has a blown head gasket. The cylinder head is still installed on the engine. What would you do first? A. Check head bolt torque. B. Magnetic flux test the cylinder head. C. Remove all residue oil, carbon, and gasket material and visually inspect for cracks D. Perform a pressure test of the head to check for internal cracks. (B3)

Question #36 Answer A is correct. When troubleshooting a suspected blown cylinder head gasket, the first step should be to check the head bolt torque values. The other answers involve steps that would be performed after the cylinder head is removed. Answer B is incorrect. Magna fluxing occurs after head removal. Answer C is incorrect. Visual inspection occurs after removal. Answer D is incorrect. Pressure testing occurs after removal.

38. Technician A says cylinder heads are always torqued in sequence according to specifications set by the manufacturer. Technician B says that any pushrods that are bent must be straightened. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B7)

Question #38 Answer A is correct, Only Technician A is Correct in describing how manufacturers want cylinder-head bolts torqued. Answer B is incorrect. It is essential that bent push tubes be replaced rather than straightened. When straightened rods are returned to service, they fail quickly and can cause severe and expensive engine damage. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

39. An engine produces a deep-sounding thumping noise that is especially noticeable at slow pm and high engine loads. Technician A says this could be caused by worn crankshaft main bearings. Technician B says that this could be a bottom-end knock caused by a failed rod big-end journal. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A4)

Question #39 Answer B is correct. Only Technician B is correct. The description perfectly describes what is often called "bottom-end" or "big-end knock. This condition is caused by a failed connecting rod bearing. Answer A is incorrect. Worn crankshaft main bearings are unlikely to cause the thumping noise described. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

4. Which of the following is LEAST-Likely to be a symptom of a mechanical governor problem? A. random engine miss B. high idle overrun C. low idle underrun D. a hunting condition (Fl.6)

Question #4 Answer A is correct. This is the LEAST-Likely symptom of a governor problem. Answer B is incorrect. Governor response timing can cause high idle overrun. Answer C is incorrect. LOW 1dle underrun is normally a symptom of a governor problem. Answer D is incorrect. Hunting can be caused by governor differential lever slop.

40. A bus enters the repair shop with damaged engine door wiring for the taillights. Technician A says repair the wiring and place the vehicle back in service. Technician B says missing engıne door stops may have caused the wiring damage. Who is correct? A. A only B. B only C. Both A and B D. Neither A or B (A17)

Question #40 Answer B is correct. The correct answer is B. Only Technician B is correct. Although the engine door wiring needs to be repaired, the cause of the damage must be found and corrected first. A common cause of engine door wiring damage is missing door stops or bumpers. If missing, the engine door may close too far and allow fan belts and pulleys to come in contact with the wiring, causing damage. If not found and corrected, the repaired wiring will only be damaged again when the vehicle is placed back into service. Answer A is incorrect. The cause of the damage must also be found and corrected. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

41. A vehicle with mechanical fuel controls is being checked for a sticking throttle complaint. Technician A says the lever return springs may be weak. Technician B says there may be air in the fuel lines. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F1.5)

Question #41 Answer A is correct. Only Technician A is correct. On mechanically controlled engines, the throttle lever controls the engine's speed. Actuation may be by linkage, cables, or air-operated actuators. The throttle return to idle speed position is controlled by a return spring. If the spring becomes broken or weak, the throttle may not return to idle speed, causing a sticking throttle condition. Answer B is incorrect. Aerated fuel will cause engine performance problems, but will not cause RPMS to hang above idle speed. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

42. Technician A says that the customer data programming can be changed in electronic systems with a PC and proprietary software. Technician B says in some cases changing data programming could result in less efficient engine performance. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.8)

Question #42 Answer C is correct. Both Technicians A and B are correct. Customer data programming can be changed using a PC and proprietary software, though some or all fields may be password protected. Changing customer data programming options can result in less efficient engine performance because, dependıng on the system, engine parameters such as peak torque, torque rise, rated power rpm, and rated power itself can be changed. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

43. Technician A says to use a straightedge across the exhaust manifold surfaces to align separate cylinder heads on the engine block. Technician B says to blow out head bolt holes to ensure bolts do not bottom-out prematurely. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B2)

Question #43 Answer C is correct. Both Technicians A and B are correct. Technician A is describing a correct method of aligning cylinder heads on a multi cylinder head engine. Technician B is also correct because bolt threads should be free of dirt, which could bind in the threads. and free of oil or other fluids, which could cause hydrostatic lock. On in-line multi cylinder heads. separate heads must be aligned with a straightedge across the intake manifold faces before torquing. Failure to observe torquing increments and sequencing can result in cracked cylinder heads, failed head gaskets, and fire rings that will not seal. Because of the large number of fasteners involved, a click-type torque wrench should be used. Some OEMS require that a torque-turn be used. This requires setting a torque value first and then turning a set number of degrees beyond that value using a template or protractor. Cylinder head bolts should be lubricated according to manufacturer specifications, although excessive quantities of oil should be avoided because the excess can drain into the bolt hole and cause a hydraulic lock. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

44. Technician A says by using a pressure relief valve in the surge tank, the boiling point of the coolant is raised. Technician B says that antifreeze raises the boil point of water. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D8)

Question #44 Answer C is correct. Both Technicians A and B are correct. For each 1 psi that a liquid is pressurized above atmospheric pressure, its boiling point raises 3°F at sea level. Most diesel engine cooling systems maintain a system pressure of 10-20 psi through the use of a relief valve in the radiator surge tank, so Technician A is correct. Antifreeze, when mixed with water, lowers the freeze point and raises the boil point so Technician B is also right. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct

45. Technician A says a testing instrument panel oil pressure gauge should closely follow a master gauge. Technician B says test readings should be taken and compared during startup, varyıng operating ranges, and on shutdown. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A15)

Question #45 Answer C is correct. Both Technicians A and B are correct. A test gauge is used to verify readings produced by the dash panel instrumentation. Technician A is correct. The readings for both the dash and master gauges should be identical. If not, the operation of the dash gauge/signal/sensor circuit will have to be checked. Technician B is also correct in saying that test readings should be taken through a range of operating rpms. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

46. The piston shown above came from an in-line 6-cylinder diesel engine equipped with electronic unit injection. All the other pistons showed normal wear. This was the only piston showing damage. Which of the following is the Most-Likely cause? A. worn exhaust cam lobe B. restricted exhaust system C. restricted air cleaner D. worn injector cam lobe (C15)

Question #46 Answer A is correct. The piston illustrated was subject to excessive cylinder temperatures. Because all the other pistons did not show this wear, the problem must be a single cylinder issue. A worn exhaust lobe would prevent the exhaust gasses from escaping the cylinder on the exhaust stroke, thus creating excessive cylinder temperatures in a single cylinder. Answer B is incorrect. A restricted exhaust system could cause excessive cylinder temperatures; however, all cylinders would be affected. Answer C is incorrect. A restricted air cleaner could also cause excessive cylinder temperatures; however, it would affect all cylinders. Answer D is incorrect. A worn injector lobe would affect only one cylinder, but it would not cause high temperature. It would cause cooler temperatures because little or no fuel would be injected.

48. On a vehicle with an electric fuel shut-off valve, which of the following would not be part of the circuit? A. fuel pressure sensor B. key switch C. solenoid armature D. solenoid coil (F1.2)

Question #48 Answer A is correct. The fuel pressure sensor would not be part of the shutdown solenoid circuit. Answer A is incorrect. A fuel pressure sensor can be part of the circuit. Answer B is incorrect. The key switch can be part of the circuit. Answer D is incorrect. The solenoid coil can be part of the circuit.

49. A mechanically controlled engine will crank but will not start. If ether is used, the engine oil will run for a few seconds, and then die. What could be the Most-Likely cause? A. a clogged air filter B. a defective fuel shut-off solenoid C. low engine oil level D. a bad starter (F1.11)

Question #49 Answer B is correct. If the fuel cut-off solenoid is not actuating, the fuel pump/injectors will not receive any fuel and the engine will not start. Answer A is incorrect. If the air filter was clogged enough to prevent the engine from starting, it would not run when ether was used. Answer C is incorrect. Low oil level will not prevent the engine from starting. Answer B is incorrect. If the starter was defective, the engine would not even crank.

5. What is being indicated on the camshaft in the figure? A. intake cam lif B. exhaust cam lift C. camshaft endplay D. cam main journal runout (B11)

Question #5 Answer D is correct. The camshaft main journal runout is being indicated while the shaft is rotated on V-blocks. Install the camshaft in V-blocks and check for shaft bending using a dial indicator. Answer A is incorrect. The intake lobe is not being measured. Answer B is incorrect. The exhaust lobe is not being measured Answer C is incorrect. Camshaft end play is measured with the cam installed.

50. What is being performed in the figure? A. clutch face surface runout B. pilot bore radial runout C. crankshaft radial runout D. flywheel housing concentricity (CI8)

Question #50 Answer A is correct. To check flywheel runout, mount a dial indicator with a magnetic base on the flywheel housing, and check the flywheel runout at the clutch contact face. The typical allowable runout is .001 in. per inch clutch radius (0.001 mm per millimeter of clutch radius). Measure the radius from the center of the flywheel to the outer edge of the clutch contact face. For example, a 14-in. (355 mm) clutch would have a 7-in. (177 mm) radius and allow a 0.007-in. (0.177 mm) total indicator reading of the dial indicator. If the measured values fall out of these specifications, repeat the assembly process and re measure until a cause can be determined. In the figure, the dial indicator is mounted to measure the clutch face surface runout, so the clutch bolts to the flywheel. Answer B is incorrect. The pilot bore is not being measured. Answer C is incorrect. Crankshaft radial runout is not being checked. Answer D is incorrect. This is not the flywheel housing concentricity check.

51. An EGR-equipped vehicle is being checked for overheating. Technician A says the EGR cooler may be clogged, causing the engine to overheat. Technician B says the EGR valve may be leaking, allowing EGR flow all the time. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (E7)

Question #51 Answer D is correct. Neither technician is correct. If the EGR cooler were clogged, the only symptom would be little or no EGR flow into the intake. The engine would not overheat, but emissions would be affected. If the EGR valve were leaking, causing EGR flow all the time, the most noticeable symptoms would be reduced boost pressure, a decrease in engine performance, and possibly rough running, but the engine should not overheat. Answer A is incorrect. Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. Answer C is incorrect. Neither technician is correct.

52. Which of the following would LEAST-Likely cause excessive backlash in the timing gear train? A. worn idler gear bearings B. Worn gear teeth C. worm camshaft bearings D. incorrect timing mark alignment (C10)

Question #52 Answer D is correct. Although proper gear timing is essential to proper engine operation, incorrect timing mark alignment would not create excessive backlash. If gear timing marks are not aligned, excessive engine damage can result from valve to piston contact. Answer A is incorrect. Worn idler gear bearings can cause excessive backlash. Answer B is incorrect. Worn gear teeth can cause excessive backlash Answer C is incorrect. Worn camshaft bearings can cause excessive backlash.

53. What should be used to measure ring-to-groove clearance? A. Plastigage B. micrometer C. feeler gauges D. dial bore gauge (C13)

Question #53 Answer C is correct. The clearance should be measured between the ring and the side of the piston ring groove with the appropriate thickness feeler gauge. If the clearance is too great, ring and land damage can result. If the clearance is too little, the rings may not fit into the grooves properly, preventing piston installation. Answer A 1s incorrect. Plastigage is used to measure bearing to journal clearances. Answer B is incorrect, Micrometers are used to measure thickness, not clearance between parts. Answer D is incorrect. Dial bore gauges are used to measure cylinder diameters.

54. All of the following are used to determine battery performance and condition EXCEPT: A. multimeter B. carbon pile load tester C. refractometer D voltage drop from battery post to positive terminal (G2)

Question #54 Answer D is correct. The voltage drop test described is used to check the condition of the connection between the battery post and positive terminal so this is not a battery test. Answer A is incorrect. A multimeter can be used to determine state of charge. Answer B is incorrect. A carbon pile load tester can be used to test the ability of a battery to deliver sufficient amperage. Answer C is incorrect. A refractometer can be used to test a battery.

55. Technician A says hat oil in a head bolt hole in the block can throw off the torque setting of that bolt. Technician B says that a head bolt with stripped threads should be dressed before installing. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C2)

Question #55 Answer A is correct. Only Technician A is correct. Oil trapped in blind bolt holes can cause hydrostatic lock when the bolt is installed and invalidate torque readings. Answer B is incorrect. A cylinder head bolt with any visible damage should be replaced not repaired. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

56. In the figure, the technician is checking the turbocharger for A. radial runout B. Turbine shaft endplay C. turbine fin wear D. compressor fin wear (E2)

Question #56 Answer B is correct. In the figure, the dial indicator is located to check turbine shaft endplay. Answer A is incorrect. Radial runout is checked by installing the dial indicator through the oil feed or oil drain hole and moving the shaft up and down. Answer C is incorrect. Turbine fin wear is checked with a visual inspection. Answer D is incorrect. Compressor fin wear is checked by visual inspection.

57. An engine equipped with a pump-line-nozzle (PLN) fuel system, cranks, but fails to start and the operation of the primer pump fails to build pressure. Which of the following would MOST-Likely cause this condition? A. injector nozzle valve seized B. primary fuel filter housing leak C. restriction in the high-pressure line to the injector D. lines between the prime pump and the injection pump restricted (F1.3)

Question #57 Answer B is correct. The Most-Likely cause of this problem would be a leak at the primary filter housing allowing air to enter the fuel system. Answer A is incorrect. A single seized injector nozzle would not cause the transfer pump to fail to build pressure and it would not prevent the engine from starting. Answer C is incorrect. A restriction in the high-pressure line between the injector pump and injector would cause a single cylinder problem. Answer D is incorrect. Restricted lines after the prime pump may cause a no-start condition; however, the hand-primer pump would build pressure.

58. Technician A says that when performing a starter load test, you should not crank the engine for more than 30 seconds at a time. Technician B says you must perform this test with a battery charger connected to the battery. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (G8)

Question #58 Answer A is correct. Only Technician A is correct, A diesel engine should never be cranked for a period exceeding 30 seconds for any reason. Answer B is incorrect. Technician B is incorrect. A starter load test should be performed using the chassis batteries without any kind of external assist. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

59. An air intake is being checked for a restriction using a water manometer. Technician A says that if the air restriction is excessive, the filter may need to be inspected. Technician B says that the engine speed should be at full load and full rpm to take the readings. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A7)

Question #59 Answer C is correct. Both Technicians A and B are correct. Checking the air intake system for Restriction is a common method of assessing the serviceability of the air filter in that high readings will indicate a plugged filter, so Technician A is correct. Technician B's statement about taking the readings at high full load is correct. Maximum inlet restriction should be measured at rated speed with the engine fully loaded. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

6. While discussing a turbocharged diesel engine, Technician A says that an exhaust manifold leak will affect the performance of the engine. Technician B says that leaks in the intake pipe can cause damage to the turbo impellor. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A12)

Question #6 Answer C is correct. Both Technicians A and B are correct. A leak in the exhaust manifold can affect performance in a turbocharged diesel engine so Tech A is correct. Leaks upstream from the turbo compressor housing can damage the impellor by allowing abrasives to enter the air intake so Technician B is also right. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

60. If an injector sleeve (tube) is found to be leaking, which of following procedures is LEAST-Likely to be required? A. replacement of the sleeve B. performing a cylinder head pressure test C. checking nozzle-tip protrusion D. replacing the injector nozzle (B5)

Question #60 Answer D is correct. The injector nozzle would not need to be replaced. So it is the LEAST-Likely to be required. Answer A is incorrect. Leaking sleeves must be replaced. Answer B is incorrect. Leaking injector sleeves (tubes) are a relatively common failure. In most cases, engine coolant comes into direct contact with the sleeve so coolant leakage problems result. When injector sleeves are found to be leaking, the sleeve should be replaced, the cylinder head should then be hot pressure tested. Answer C is incorrect. Because nozzle-tip protrusion is dependent on the precise location of the injector sleeve, this should also be measured. The injector nozzle has nothing to do with the reasons for replacing the cylinder sleeve so this is the least item to be replaced.

61. The figure shows what type of fan hub? A. air clutch fan hub B. electrically activated fan hub C. thermatic fan hub D. hydraulic fan hub (D14)

Question #61 Answer C is correct. The figure shows a thermatic fan, one in which effective cycle is managed by a bimetal strip connected to a valve, which in turn controls silicone media to manage lock-up and free-wheel cycles. Answer A is incorrect. This is not an air clutch. Answer B is incorrect. This is not an electric clutch. Answer D is incorrect. This is not a hydraulic clutch.

62. An engine with a distributor-type injector pump cranks, but fails t0 start. Which of the following could be a possible cause? A. a defective injector B. a defective starter cut-out relay C. a defective shutdown solenoid D. a leaking air intake hose (F1.6)

Question #62 Answer C is correct. A defective shutdown solenoid can cause no fuel delivery to the engine, resulting in a no-start condition. Failure of the fuel shutdown solenoid is a relatively common problem in distributor pumps, allowing the engine to crank but not receive any fuel. Answer A is incorrect. One defective injector will usually not prevent a multi cylinder engine from starting. Answer B is incorrect. This engine cranks so the starter cut-out relay is not the cause of the problem. Answer D is incorrect. A leaking air intake hose would not cause a no-start condition.

63. Technician A says a radiator cap in a cooling system that cannot maintain its rating pressure can cause an overheat condition. Technician B says when the pressure exceeds its rating, the cap relieves the pressure. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D13)

Question #63 Answer C is correct. Both Technicians A and B are correct. A cooling system's boil point 1s increased by holding it under pressure. If the pressure cannot be maintained, the coolant can boil at a lower temperature. Boiling coolant within a cooling system accelerates an overheat condition because a gas does not conduct heat as well as a liquid. The radiator cap is designed to relieve system pressure when it exceeds its rating. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

64. On a diesel engine with a charge-air cooler, a technician notices soot in the intake manifold. What should the technician check first? A. intercooler B. turbocharger C. intake manifold D. head gasket (E2)

Question #64 Answer B is correct. The probable source of soot in the intake manifold of a turbocharged, charge air-cooled diesel is the turbocharger itself. The condition is usually caused by passing oil getting heated in the hot, turbo-boosted air. Some soot in the intake manifold is normal in most diesel engines; it usually indicates an engine operated at low loads and speeds for prolonged periods. In such operating conditions, the valve overlap duration is at a maximum in real-time values and manifold boost is minimal or nonexistent. Excessive soot in the intake manifold may indicate imminent turbocharger failure or an injection timing problem. Answer A is incorrect. The intercooler cannot cause soot in the intake manifold. Answer C is incorrect. The intake manifold cannot cause soot inside itself. Answer D is incorrect. The head gasket could not cause soot to build up in the intake manifold.

65. After the technician cleans a disassembled engine block, what should be done next? A. paint the exterior B. magnetic flux test for cracks C. remove the cylinder sleeves D. plug all oil ports (C2)

Question #65 Answer B is correct. When a major diesel engine overhaul is performed, it is good practice to thoroughly inspect the cylinder block using magnetic flux inspection. Answer A is incorrect. The painting would take place after it had passed magnetic flux crack detection. Answer C is incorrect. The cylinder sleeves would be removed before cleaning. Answer D is incorrect. Plug installation would take place after magna fluxing. It makes sense to magnetic flux test engine cylinder blocks, crankshafts, and all connecting rods at every major engine overhaul. These processes are neither expensive nor time consuming and as the consequences of a single warranted engine failure out of 20 overhauls will demolish the profits of the other 19, it is shortsighted to overlook it.

66. When the oil filter by-pass valve opens, what has caused it to do so? A. restricted inlet to the filter B. the oil pump is sucking air C. massive oil leak in the lubrication system D. filter element is plugged (D3)

Question #66 Answer D is correct. When the by-pass valve trips on an oil filter pad assembly, the oil is routed around the filter assembly; that is, it bypasses it. This will only occur when the filter element has become plugged. Filter-mounting pad by-pass valves operate in much the same way as the oil pressure regulating valves, except that their objective is to route the lubricant around a restricted full-flow filter to prevent engine damage by oil starvation. When a filter by-pass valve is actuated and the check valve unseated, instead of spilling the oil to the crankcase, it reroutes the oil directly to the lubrication circuit, effectively shorting out the filter assembly. So, when a by-pass value trips, unfiltered oil is circulated through the lubrication circuit. Answer A is incorrect. A restricted inlet would cause insufficient oil to the filter. Answer B is incorrect. If the oil pump was sucking air, pressure would be low. Answer C is incorrect. A massive oil leak would lower pressure, not raise it.

67. The rear two cylinders on an in-line 6-cylinder engine show eroded piston wear. Technician A says this could be caused by low water pump flow. Technician B says this could be caused by dirty oil. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D12)

Question #67 Answer A is correct. Only Technician A is correct. When an engine shows wear only in a specific portion and the rest of the engine looks normal, the technician should concentrate the diagnostic routine on items that affect that part of the engine only. At first glance, both items mentioned would seem to affect the entire engine; therefore, they are not very likely to cause damage to only the rear two cylinders. If a diesel engine was operated with dirty oil, then all the bearing surfaces should be worn. All cylinders would be affected if the water pump produced inadequate flow, but the rear two cylinders would be the most affected due to distance from the pump. Technician A is correct. Answer B is incorrect. Dirty oil would most likely affect the entire engine. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

68. Which of the following is LEAST-Likely to produce a loss of power in a diesel at full-rated loads? A. high exhaust back pressure B. high manifold boost pressure C. oil and dirt in the air tubes or cooling fins of the aftercooler D. small leak in the fuel line from the tank to the pump (A12)

Question #68 Answer B is correct. High manifold boost increases the air density and the potential to produce high power so this would be the LEAST-Likely cause of a lack of power complaint. Answer A is incorrect. High exhaust back pressure would cause low power and overheating. Answer C is incorrect. Clogged cooling fines would cause high air inlet temperatures that would reduce horsepower. Answer D is incorrect. A small leak in the suction fuel line would cause low power.

69. Technician A says that a won diesel engine lube pump may cause low oil pressure. Technician B says that the high-pressure oil pump used on HEUI systems uses a swash plate principle. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D2)

Question #69 Answer C is correct. Both Technicians A and B are correct. Worn engine lube pumps can cause low oil pressure. HEUI high-pressure oil pumps do use a swash plate (wobble plate) principle. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

7. Technician A says that when replacing a wet-type sleeve, you should always replace the O-rings. Technician B says that new O-rings should be coated with anaerobic silicone. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C5)

Question #7 Answer A is correct. Only Technician A is correct. O-rings on wet liners should be changed any time the sleeve is pulled and reinstalled. Answer B is incorrect. The manufacturer's recommendation for coating wet sleeve O-rings should be observed. This could mean nothing at all, soap, antifreeze, and usually not anaerobic silicone. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

70. Technician A says that main bearing shells should receive a light coat of oil on both the face and back before final installation. Technician B says that when checking the bearing, install Plastigage in all the bearings, torque to specifications, and rotate the crankshaft. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C9)

Question #70 Answer D is correct. Neither technician is correct. Bearing shells should be installed to the bore clean and dry to optimize heat transfer between the bearing material and the bore. A thin coat of oil may be applied to the bearing face only. When Plastigage is used to check bearing clearance, it is important that the crankshaft not be rotated. Plastigage is soft plastic thread that easily conforms to whatever clearance space is available when compressed between a bearing and journal. The crushed width can then be measured against a scale on the Plastigage packaging. The less clearance available will result in the Plastigage being flattened to a wider dimension. A short strip of Plastigage should be cut and placed across the center of the bearing in line with the crankshaft. The bearing cap with the bearing shell in place should then be installed and torqued to specification in the incremental steps outlined in the workshop manual. Do not rotate the engine with the Plastigage in place. Next, the bearing cap and shell should be removed and the width of the flattened Plastigage checked against the dimensional gauge on the packaging. If clearance is within specifications, carefully remove the Plastigage from the journal before reinstalling the cap and shell assembly. Answer A is incorrect. Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. Answer C is incorrect. Neither technician is correct.

72. What type of air cleaner is shown in the figure? A. oil bath B. dry type C. centrifugal D. precleaner (E1)

Question #72 Answer B is correct. The figure shows a dry-type, positive filtration, air filter assembly. This type of filter has high efficiencies because all of the air has to pass through the filtering media to get into the intake system. Some dry element filters are two-stage and may eliminate the need for a precleaner; these induce a vortex flow and use centrifugal force to separate heavier particulate, which is then discharged by an ejector valve. Answer A is incorrect. This is not an oil bath air cleaner. Answer C is incorrect. This is not a centrifugal air cleaner. Answer D is incorrect. This is not a precleaner.

73. Technician A says the cylinder head should be checked for warpage with a dial indicator. Technician B says that the wrist pins should be checked for wear with a dial indicator. Wh0 IS Correct? A. A only B. B only C. Both A and B D. Neither A nor B (B3)

Question #73 Answer D is correct. Neither technician is correct. Answer A is incorrect. Heads are checked for warpage with a straightedge and feeler gauge. Answer B is incorrect. Wrist pins are checked for wear with an outside micrometer. Answer C is incorrect. Neither technician is correct.

74. While discussing a low voltage problem at the starter, Technician A says that a corroded battery cable may be the cause. Technician B says that a defective starter drive may be the cause. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (G5)

Question #74 Answer A is correct. Only Technician A is correct. One lead of the voltmeter is connected to the ground terminal of the battery and the other lead is connected to the base of the starter. Then the voltmeter is read while the engine is cranked. If the voltage reading exceeds 0.2 volt, excessive resistance exists in the ground circuit. Answer B is incorrect. A defective starter drive is a mechanical problem that would not affect the voltage at the starter. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

75. A vehicle is found to have high exhaust back pressure and elevated exhaust temperature. Technician A says this is caused by a DPF that needs to be serviced. Technician B says a caused by a burned exhaust valve. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A9)

Question #75 Answer A is correct. Only Technician A is correct. The DPF needs to be serviced. DPFS are designed to trap and collect solid matter, such as soot and ash, present in the exhaust. As these solids accumulate, the exhaust flow through the DPF will be reduced, creating high back pressure and temperature levels. When the DPF reaches this point, it must be either removed and cleaned, following manufacturer's procedures, or replaced. Answer B is incorrect. While a burned exhaust valve can cause elevated exhaust temperatures by allowing unburned fuel to enter the catalyst assembly and generate high internal temperatures, it would not cause an increase in back pressure. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

76. When rebuilding an engine, Technician A says the viscous crankshaft damper should always be replaced. Technician B says cracks in the damper can be welded and the damper reused. who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C16)

Question #76 Answer D is correct. Neither technician is correct. Answer A is incorrect. While some manufacturers recommend replacing the damper during engine rebuilds, some manufacturers allow reuse after careful inspection for damage. Service manuals should be consulted for determination of reuse. Answer B is incorrect. No manufacturer will allow repairing of the damper, especially welding of cracks. The job of the damper is to remove vibration and help balance the crankshaft, and welding could add an imbalance to the crankshaft, causing premature failure of the crankshaft. Answer C is incorrect. Neither technician is correct.

77. An electronically controlled diesel engine runs poorly. It has 8 active codes and 10 inactive codes. All the codes were set at the same ECM time. Which of the following is the most likely cause? A. worn crankshaft thrust washer B. worn camshaft thrust washer C. poor electrical supply connections D. faulty ECM (F2.9)

Question #77 Answer C is correct. An electronically controlled diesel engine should set active codes for systems or sensors that are currently operating outside of preprogrammed parameters. An example would be an out-of-range coolant temperature sensor. If several codes are all set at the same time. it is highly likely there 1S a common cause. In this situation the most reasonable diagnostic course would be to check for adequate power and ground to the ECM. Answer A is incorrect. A worn crankshaft thrust washer would most likely set only a cranksha position sensor code. Answer B is incorrect. A worn camshaft thrust washer would most likely only set a camshaft position sensor code. Answer D is incorrect. It is highly unlikely the ECM is faulty.

78. A camshaft fails to pass visual inspection. Technician A says damaged camshaft bearing surfaces can be turned. Technician B says flat spots on lobes can be silver soldered and machined to original specifications, Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B11)

Question #78 Answer D is correct. Neither technician is correct. Damaged camshaft bearing surfaces should not be turned and diesel engine camshafts are never repaired with silver solder. The technician should be aware that the smallest indication of a hard-surfacing failure on the cam profile requires little time to advance to a total failure. Answer A is incorrect. Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. Answer C is incorrect. Neither technician is correct.

79. Before installing the valves into the cylinder head it is important to check which one of the following? A. valve-to-seat contact B. rocker arm adjustment C. camshaft lift D. head gasket (B7)

Question #79 Answer A is correct. Before installing valves into a cylinder head, seat contact should be tested with Prussian blue. Check also for the correct pattern on the valve face. The remainder of the procedures would be performed after the cylinder valves had been installed in the head. Answer B is incorrect. Rocker arms are adjusted after the head is installed. Answer C is incorrect. Measuring camshaft lift is checked while inspecting the camshaft. Answer D is incorrect. Head gaskets are checked during disassembly for evidence of leaks. Head gaskets are replaced. They are not reused.

8. Technician A says that excessive crankcase pressure can be caused by a plugged oil breather. Technician B says that all diesel engines use exhaust gas recirculation (EGR). Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A10)

Question #8 Answer A is correct. Only Technician A is correct. High crankcase pressures can be caused by a plugged oil breather. Answer B is incorrect. Technician B is incorrect in saying that all diesel engines use exhaust gas recirculation (EGR), although some do and more will as nitrides of oxygen (NOx ) emissions continue to be a problem for truck diesel engine designers. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

80. When installing a camshaft into the cylinder block, the technician finds it is hard to turn, Which of these could be the LEAST-Likely cause? A. the camshaft is bent B. the camshaft bore is out of line C. bearing-to-journal clearance is incorrect D, the camshaft gear was not installed prior to camshaft installation (C7)

Question #80 Answer D is correct. While some engine manufacturers require that gear installation be performed before the cam is installed, some do not. Either way, the presence of the gear will have no affect on the bearing clearance or alignment. Answer A is incorrect. If the camshaft is bent, it will bind in the bore and cause it to lock. Answer B is incorrect. If the camshaft bearing bores are not in-line, the cam will bind and be hard to turn. Answer C is incorrect. If there is insufficient clearance, the cam will bind and be hard to tum. This condition will also cause bearing and camshaft damage.

81. An electronically controlled diesel engine will start but will only idle. Technician A says a faulty intake air temperature sensor could cause this. Technician B says a faulty TPS could cause this. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.2)

Question #81 Answer B is correct. Only Technician B is correct. If a computer-controlled diesel engine will start but not accelerate, the most likely problem is a fault in the throttle position sensor circuit. The ECM does not recognize that the operator wants to increase engine speed. Answer A is incorrect. The intake air temperature sensor helps the computer tim the fuel quantity and timing to produce the cleanest burn under all incoming air temperatures. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

82. The cylinder head deck-to-deck thickness measurement indicated in the figure is used A. prevent cylinder head warpage. B. calculate valve guide height. C. determine cylinder warpage. D. determine resurfacing limit. (B3)

Question #82 Answer D is correct. Minimum head "deck-to-deck" thickness is critical. If a cylinder head is machined below this minimum specification, it will be much more likely to crack due to its now thinner casting. Additionally, when the head becomes thinner, critical valvetrain geometry angles are changed. The figure indicates how much machining can be sustained while meeting the minimum head deck-to-deck specification. Answer A is incorrect. This measurement does not prevent head warpage: however. if a head is too thin it will be prone to warpage. Answer B is incorrect. Valve guide height is measured on the valve guide. Answer C is incorrect. Cylinder head warpage is determined with a straightedge and feeler gauge.

83. Which is LEAST-Likely to be used to check connections on the electronic circuits? A. digital ohmmeter B. digital multimeter C. test light D. breakout box (F2.6)

Question #83 Answer C is correct. It is bad practice to use a test light on electronic circuits, so this should be the LEAST-Likely. A test light can draw too much amperage. Answer A is incorrect. A digital ohmmeter is a good tool to use on an electronic circuit. Answer B is incorrect. A digital multimeter is a good tool to use on an electronic circuit. DMMS are simple tools for taking electrical measurements. DMMS may have any number of special features but essentially, they measure electrical pressure or volts, electrical current flow or amps, and electrical resistance or ohms. A good-quality DMM with minimal features may be purchased for as little as $100; as the features, resolution, and display quality increase in sophistication, the price increases proportionally. Because most electronic circuit testing requires the use of a DMM, this instrument should replace the analog multimeter and circuit test light in the truck/bus technician's toolbox. Reliability, accuracy, and ease of use are all factors that should be considered when selecting a DMM for purchase. Some options the technician may want to consider are a protective rubber holster (will greatly extend the life of the instrument!), analog bar graphs, and enhanced resolution. Answer D is incorrect. A breakout box is a good tool to use on an electronic circuit.

84. In the customer data programming options in the software of an Electronic Service Tool (EST). the technician can select between LS and VS governing. Which option would make the vehicle accelerator pedal respond similarly to the accelerator pedal in an automobile? A. LS B. VS C. no difference D. both options would have to be selected (F2.8)

Question #84 Answer A is correct. LS (limiting speed) governing means that accelerator pedal angle is correlated to fuel quantity. If more fuel is required, for instance to climb a hill, the pedal angle must be increased. This action/response is similar to the accelerator pedal in a car. Answer B is incorrect. A variable speed (VS) governor is known as an all-speed governor in the United Kingdom. It sets engine idle speed and defines high idle and any speed in the intermediate range, depending on accelerator pedal position. Answer C is incorrect. Answer D is incorrect.

85. A bus driver requests that logged incidents of engine overspeed and panic braking be removed from the engine ECM audit trails. Technician A says that he can do this by erasing all logged data using a PC and proprietary software. Technician B says that this can also be done by replacing the ECM PROM chips. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.1)

Question #85 Answer D is correct. Neither technician is correct. Audit trails are designed to provide a profile of vehicle handling data for later analysis and cannot be erased in the same way as historic fault, so Technician A is incorrect. Technician B is also incorrect. Audit trails are not written to PROM, they are logged in EEPROM. Also, because of EEPROM capability, PROM chips are not replaceable in current diesel engine management systems. Answer A is incorrect. Technician A is incorrect. Answer B is incorrect. Technician B is incorrect. Answer C is incorrect. Neither technician is correct.

86. A camshaft fails to pass visual inspection. Technician A says you cannot machine defective camshaft bearing surfaces. Technician B says you visually inspect the camshaft gear for cracks, chips, and broken teeth. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B11)

Question #86 Answer C is correct. Both Technicians A and B are correct. Diesel engine manufacturers do not recommend any machining procedures on camshafts. The camshaft gear must be visually inspected to assess its serviceability. Visual inspection should be sufficient to determine the condition of timing gears. Any indications of cracks, pitting, heat discoloration, or chipping of the gear teeth will predicate its replacement. Press-fit gears will require the use of a mechanical. pneumatic, or hydraulic puller to remove the gear from the shaft. Answer A ís incorrect. Technician B is also correct, Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

87. What is being done in the figure? A. A voltage drop test. B. The locking tang is being released. C The terminal blades are being spread. D. A digital multimeter test probe is being inserted. (A3)

Question #87 Answer B is correct. When replacing connectors, ensure that each wire is labeled by cavity location to facilitate reassembly. Use strips of masking tape on wires to write each cavity code on. This is usually easier than reassembling a multi wire connector using the OEM wiring schematic. The figure shows a Weather-pack type connector into which a release tool is being inserted to release the lock tang. Answer A is incorrect. This is not a voltage drop test. Answer C is incorrect. The terminal blades are not being spread; the locking tang is being released. Answer D is incorrect. The figure does not show a digital multimeter test probe being inserted; it shows a release tool being inserted. A digital multimeter test probe should not be inserted into the cavity as it will most likely spread the cavity open, resulting in a poor electrical connection when the mating connector is reconnected.

89. Technician A says that a typical throttle position sensor is connected to a 5-volt reference. Technician B says when the accelerator is depressed, signal voltage will rise above 5 volts. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.2)

Question #89 Answer A is correct. Only Technician A is correct. Most bus TPSS are connected to V-Ref, usually 5 VDC. (Remember, one of the major engine manufacturers powers up its TPS with 8 VDC to output a PWM signal.) Answer B is incorrect. The TPS is a potentiometer or voltage divider, so only a portion of V-Ref is returned as a signal. That would result in values always less than 5 VDC. The critical sensor in the electronic foot pedal assembly (EFPA) is the throttle position sensor (TPS). The TPS receives reference voltage (V-Ref) of 5 V and returns a portion of it, proportional to pedal mechanical travel. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

9. Technician A says to use a digital voltmeter to test grounds with an energized circuit. Technician B says to use an ammeter to test grounds when power is not applied. Who is -correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.10)

Question #9 Answer A is correct. Only Technician A is correct. Voltage drop testing is a means of testing the condition of wires, cables, connections, and loads in the electrical circuit. It is a much better method of testing electrical circuit resistances because the testing is performed in a fully energized electrical circuit as opposed to checks with an ohmmeter, which must be performed on inactive circuits. Answer B is incorrect. An ammeter can only produce a reading when connected in series in an energized circuit. Answer C is incorrect. Only Technician A is correct. Answer D is incorrect. Only Technician A is correct.

90. Technician A says that temperature sensing devices used on electronically managed diesel engines are thermistors, which receive a reference voltage (V-Ref) and return a portion of it as a signal to the ECM. Technician B says that some vehicle thermistors use a negative temperature coefficient (NTC), meaning that resistance decreases as temperature goes up. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (F2.9)

Question #90 Answer C is correct. Both Technicians A and B are correct. Technician A correctly describes the operation of a thermistor. Technician B is also correct in saying that NTC thermistors are generally used in diesel engines. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

91. Which of these would be LEAST-Likely to cause low engine oil pressure? A. won bearings B. use of oil with a high Viscosity index C. restricted suction tube D. worn oil pump (A15)

Question #91 Answer B is correct. Oil with a high viscosity index changes little over a wide temperature range and therefore would be very unlikely to cause low oil pressure. Answer A is incorrect. Won bearings are a very common cause of low oil pressure. Answer C is incorrect. A restricted oil pump suction tube would cause low oil pressure, especially at higher rpms when oil flow is at the highest. Answer D is incorrect. A worn oil pump would bypass oil internally and cause low oil pressure.

92. Tech A says that a gray or black smoke from the engine exhaust could be an indication of air starvation. Technician B says that gray or black smoke can be caused by overfueling. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A5)

Question #92 Answer C is correct. Both Tech A and B are correct. A common cause of gray or black smoke is air starvation, indicating that an insufficient amount of air is in the engine cylinder to combust the fuel injected, so Tech A is correct. Overfueling can also cause gray or black smoke emission for the same reasons, so Tech B is also right. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

93. When replacing a coolant filter, Tech A says to prime the filter with coolant before installation. Tech B says to turn the service valve off before removing the old filter. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (D11)

Question #93 Answer B is correct. Only Technician B is correct. You must turn off the service valves before removing the old filter, otherwise, coolant will leak from the filter housing once the filter is removed. Turning off the valves isolates the filter housing from the rest of the cooling system. Answer A is incorrect. Most manufacturers do not recommend priming the filter before installation. Any air in the filter will be purged once the engine is started and the coolant is allowed to circulate through the filter. Coolant level should be checked after servicing the filter. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

94. In a 2 12-V battery, 12-V electrical system, how are the batteries connected? A. series circuit B. parallel circuit C. series/parallel circuit D. isolation circuit (G8)

Question #94 Answer B is correct. If both batteries are 12 volts and they supply a 12/12 electrical system, the batteries must be connected in parallel. Answer A is incorrect. A series circuit would produce 24 volts. Answer C is incorrect. A series/parallel circuit would be used with series/parallel magnetic switch in a 12/24 circuit. Answer D is incorrect. An isolation circuit typically isolates a ground on a 12/24 circuit.

95. A crankshaft is found to have fractures that may have been caused by improper alignment Technician A says to use a master bar to check the main bore alignment. Technician B says to use an inside micrometer to check the main bore diameter for an out-of-round condition, Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (C8)

Question #95 Answer C is correct. Both Technicians A and B are correct, Whenever a crankshaft is damaged, the cylinder block should be checked. The master bar is designed to check the main align bore; it is installed without bearing shells with the main caps snug. If it does not rotate freely, the block align bore requires machining. The main bores should also be checked for out-of-round and this can be done with an inside micrometer. Answer A is incorrect. Technician B is also correct. Answer B is incorrect. Technician A is also correct. Answer D is incorrect. Both technicians are correct.

96. What procedure is the technician performing on the cylinder head in the figure? A. replacing valve guide seals B. replacing valve guides C. replacing valve stems D. replacing rocker am studs (B4)

Question #96 Answer A is correct. The figure shows a technician replacing valve guide seals. Answer B is incorrect. The figure shows a technician replacing valve guide seals. Answer C is incorrect. The figure shows a technician replacing valve guide seals. Answer D is incorrect. The figure shows a technician replacing valve guide seals.

97. Tech A says that when replacing solid lifters you should also replace the timing gears. Tech B says that each lifter should be checked in its mating bore in the block to ensure proper fit. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (B9)

Question #97 Answer B is correct. Only Technician B is correct. Each lifter should be checked in its mating bore, Lifters are manufactured from cast iron and middle alloy steels and are usually located in guide bores in the cylinder block, allowing them to ride the cam profile over which they are positioned: pushrods are fitted to lifter sockets. The critical surface of a solid lifter is the face that directly contacts the cam profile. This face must be durable and may either be chemically hardened. cladded with a toughened alloy, or have a disc of special alloy steel molecularly bonded to the face. Solid lifters should be carefully examined primarily for thrust face wear at engine overhaul but also stem and socket wear. Guide bores in the cylinder block should also be measured using digital calipers or a telescoping gauge and a micrometer. SleeVing lifter guide bores is a relatively simple procedure that involves boring to an interference fit to the new sleeve's outside diameter. Always check that the lifters do not drag or cock in newly sleeved guide bores. Answer A is incorrect. There is no need to replace the timing gears simply because you replaced the lifters. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.

98. What test is being performed in the figure? A. starter motor source voltage B. voltage drop of the starter ground circuit C. voltage drop of the starter positive circuit D. resistance in the starter control circuit (G8)

Question #98 Answer B is correct. A voltage drop test is performed by placing the voltmeter leads across the portion of the circuit being tested and observing voltage with the circuit operating. In the figure, one lead is on the battery negative post; the other is attached to the starter case. The groundside of the circuit is between the voltmeter leads. The starter motor must be cranking when performing this test. Answer A is incorrect. This is a voltage drop test on the ground side of the starter. Answer C is incorrect. This is a voltage drop test on the ground side of the starter. Answer D is incorrect. This is a voltage drop test on the ground side of the starter.

99. When installing head bolts, Tech A says a service manual is the best place to find head bolt torque procedures. Tech B says to check for factory service bulletins before proceeding with any procedure. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B (A18)

Question #99 Answer B is correct. Only Technician B is correct. Factory service bulletins are the most up-to- date information available for service issues. Printed service manuals may be out of date or contain errors that would be addressed by a service bulletin. Answer A is incorrect. Ifa procedure or specification has been changed by the manufacturer after the publish date of the service manual, the information is no longer valid. Checks for updates should be made on a regular basis. Answer C is incorrect. Only Technician B is correct. Answer D is incorrect. Only Technician B is correct.