Diesel engines exam-3
Answer A is correct. A crack fuel tank pick up line can allow fuel to drain back into the tank when the engine is shut off.
1. The fuel drains back to the tank after setting overnight. Which of the following could be the cause? A. Cracked fuel tank pick up line. B. A stuck close return check valve. C. A restricted supply line. D. A restricted return line.
Answer B is correct. Only technician B is correct if the open code changed to a shorted code, then the sensor is open and should be replaced.
10. The ECM has set an open coolant temperature sensor trouble code. The technician disconnects the sensor and jumps across the two terminal connections and starts the engine. The ECM immediately set a shorted coolant temperature sensor code. Technician A says the problem could be in open wiring harness. Technician B says the problem could be an open sensor. Who is correct?
Answer B is correct. PID stands for parameter ID, and indicates that parameter is at fault.
11. Which of the following best describes a PID? A. Programmed ID. B. Parameter ID. C. Parts ID. D. Personality ID.
Answer A is correct. Only technician A is correct. High exhaust back pressure can be caused by a DPF that is restricted. The DPF can be restricted with ash or Particulates.
12. Engine exhaust back pressure is higher than specification. Technician A says a restricted diesel particulate filter (DPF) Could be the cause. Technician B says a restricted charge air cooler could be the cause. Who is correct?
Answer D is correct. Neither technician is correct
13. There are very shallow cracks in a diesel engine cylinder head running from the exhaust valve seat to the injector nozzle hole. The head is pressure tested and passes the test. Technician A says this head must be replaced. Technician B says this injector must be replaced who is correct?
Answer A is correct. Alternator amperage out but should be measured with an amp clamp around the alternator cable.
14. Which of the following is the correct way to check alternator amperage output? A. At the alternator cable with an amp clamp. B. At the ECM. C. At the ignition switch. D. With an ohmmeter.
Answer D is correct. Neither technician is correct EUI fuel system do not have delivery valves or racks.
15. A diesel engine equipped with EUI Has a single cylinder miss. Technician A says the problem could be a sticky delivery valve. Technician B says the problem could be a miss adjusted rack. Who is correct?
Answer B is correct. This internal engine compression break, in common with most, uses hydraulic forced to actuate the slave piston over the exhaust valve. Hydraulic medium is engine oil trapped in the circuit between the master piston and the slave piston.
16. Referencing the illustration shown a sectional view of an engine brake, what force acts on the exhaust valve bridge to dump cylinder pressure when the engine brake is active? A. Mechanical force from exhaust rocker movement. B. Hydraulic force acting on the slave piston. C. Electromechanical force from the solenoid. D. Inductive force from the solenoid.
Answer C is correct. Fuel level is the obvious place to start.
17. A diesel engine dies and will not start. Which of the following should the technician do first? A. Check the ECM for codes. B. Check the oil level. C. Check the fuel level. D. Measure engine temperature.
Answer C is correct. Both technicians are correct. The higher the engine speed, the greater the number of effective cycles of an internal engine compression break in a given time period. As a result, engine compression break always have higher efficiency at high RPM. The Cummins ISX engine series is capable of affecting engine break in six stages Using from between one and six engine cylinders.
18. Technician A says the internal engine compression brake are most effective when the engine is running at close to rated speed. Technician B says that some current engine brakes can be actuated in six stages, using between one and six engine cylinders to provide graduated breaking. Who is correct?
Answer B is correct. The Pistons are worn and should be replaced.
19. During reassembly, the technician finds piston ring side clearance is greater than specification. Which of the following should be done? A. Replace the piston rings. B. Replace the pistons. C. Bore the cylinder oversize. D. Knurl the piston.
Answer B is correct. The engine coolant will freeze at higher temperatures then if the coolant was correct.
2. An under concentration of anti-freeze in the coolant system can cause: A. Leaking water pump. B. Insufficient freeze protection. C. Low power. D. Excessive exhaust temperature.
Answer A is correct. The DPF is usually removed and cleaned or removed and exchanged.
20. The DPF needs to be cleaned of ash. This will most likely require: A. Removal of the DPF. B. Removal of the exhaust gas recirculation (EGR) C. Bore the cylinder oversize. D. Draining a fuel system.
Answer A is correct. If the pressure is acceptable, then the pump is capable of making pressure and is not the cause of the hard to start concern.
21. A common rail diesel engine is hard to start. If the fuel pressure is checked and found to be within specification. All of the following could be the cause of the no start except: A. Worn high-pressure pump. B. Excessive negative battery cable voltage drop. C. Worn compression rings. D. Worn injectors.
Answer D is correct. A restricted screen could allow sufficient flow at idle, but insufficient flow at high idle, leading to fluctuating pressure.
22. A diesel engine has normal oil pressure at idle and low functioning oil pressure at high idle. Which of the following could be the cause? A. Too much oil in the pan. B. Restricted oil filter. C. Wrong viscosity engine oil. D. Restricted oil pick up screen.
Answer C is correct. The APP sensor is a computer and put that sends information to the computer and is not controlled by the computer.
23. All of the following would be considered a computer output except: A. Engine break solenoid. B. Engine cooling fan relay. C. APP sensor. D. Diagnostic trouble code.
Answer A is correct. Only technician A is correct. A failed boost pressure sensor could cause the ECM to overfill the engine, resulting in black smoke.
24. A diesel engine equipped with an EUI fuel system blows excess of smoke. Technician A says the boost pressure sensor may be faulty. Technician B says the coolant temperature sensor may be faulty. Who is correct?
Answer D is correct. This is an acceptable amount of taper for reuse. Typically, taper below 0.001-0.002 inches is acceptable.
25. During overhaul, the technician finds that a cylinder bore has 0.0001 inches taper What should the technician do? A. Replace the engine block. B. Board the engine block. C. Sleeve the engine block. D. Reuse the engine block.
Answer D is correct. A problem in the low pressure fuel supply system can easily cause a low power concerned.
26. When should the technician check the pressure in the low pressure fuel supply circuit? A. Every time the fuel filters or replaced. B. Every time the air filter is replaced. C. When there is a fuel economy concerned. D. When there is a low power concern.
Answer D is correct. The computer usually sends 5 Volts to the sensor.
27. What voltage reference signals does the ECM send to the reference voltage sensors? A. 20 Volts. B. 15 volts. C. 10 volts. D. 5 Volts.
Answer C is correct. Both technicians are correct. Technician A correctly describes how to remove the surface charge from a battery that has been recently charge. A stored battery does not have a surface charge, so technician B is also correct.
28. Technician A says in order to remove the surface charge from a recently charge battery, the technician should apply a 300 amp load across the terminals for 15 seconds. Technician B says that it is unnecessary to remove the surface charge from the battery that have been in storage. Who is correct?
Answer A is correct. The pump must be time to the engine. PLN-E engine injection timing is controlled by the physical mounting position of the pump.
29. The fuel injection pump is being replaced on a pump-line-nozzle electronic (pLN-E) A. The pump must be time to the engine. B. The injectors will also be replaced, because they are a matched set. C. The inactive (history) codes must be erased before the engine will start. D. The engines camshaft position sensor must be replaced because they are a matched set.
Answer D is correct. A micrometer is not used to adjust the injector on any EUI engines.
9. When installing an injector in an engine equipped with the electronic unit injector (ECI) fuel system, all of the following tools can be used to adjust the injector except: A. Dial indicator. B. Torque wrench. C. Height gauge. D. Micrometer.
Answer A is correct. Only technician A is correct. Only the crankshaft side of the bearing should be lubricated. This lubrication helps prevent bearing damage when the engine is first started.
3. Main bearings are being installed. Technician A says the front of the bearing should be lubricated. Technician B says the back of the bearing should be lubricated. Who is correct?
Answer D is correct. Oil pressure would be low, because the Increase Clarence would reduce oil flow restriction.
30. A cam in block diesel engine has excessive cam bearing clearance. This could result in: A. Retarded camshaft timing. B. Advance camshaft timing. C. Excess of boil pressure. D. Low oil pressure.
Answer D is correct. Both cruise control and airbag systems can pass through the clock spring mounted in the steering column.
31. The cruise control will not work on a vehicle that also has an airbag warning light illuminated on the dash. Which of the following is most likely the cause? A. A faulty cruise control switch. B. A blown accessory fuse. C. Damage airbag acceleration sensor. D. Damage clock spring.
Answer C is correct. A faulty boost pressure sensor could give false information to the ECM, resulting in too much fuel and black smoke.
32. A diesel engine produces black smoke during acceleration, but runs OK otherwise. Which of the following is the most likely cause? A. Low turbo boost. B. Restricted exhaust. C. Faulty boost pressure sensor. D. Restricted fuel filter.
Answer A is correct. Restrictive coolant passage could restrict flow just to the rear of the engine.
33. The rear two cylinders on an in-line six cylinder engine are worn much worse than the others which of the following could be the cause? A. Restricted coolant passages. B. Low fuel pressure. C. Restricted fuel passage. D. Loose intake valve adjustment on those two cylinders.
Answer B is correct. Only technician B is correct. It is important to maintain correct voltage to the scan tool during this process. If scan to voltage drops below minimum, the scan tool can shut down and corrupt the file.
34. The ECM has several unrelated and authorize DTCs. A technician service bulletin instruct the technician to reflash the ECM. Technician A says that during the reflash, a battery charger should be connected to the vehicle battery and set on the boost setting. Technician B says the scan tool used for the reflash should be connected to an auxiliary power supply to ensure voltage to the scan tool is not interrupted. Who is correct?
Answer C is correct. The Wastegate adjusted should not have been affected by replacing the head.
35. The cylinder head has been replaced on the engine. All of the following need adjusted except: A. Intake valves. B. Exhaust valves. C. Waste gate. D. The compression break.
Answer B is correct. Battery potential is checked by measuring open circuit voltage with a voltmeter.
36. To determine battery potential (state of charge) On a sealed battery, which measuring instrument is use? A. Refractometer. B. Voltmeter. C. Ohmmeter. D. Ammeter.
Answer A is correct. Only technician A is correct a loss of voltage during reprogramming can lock the ECM and permanently damage it. In many cases, the only solution is to replace the ECM.
37. While program in the ECM on a truck, battery voltage drop to 11.0 volts and the re-programming failed. Technician A says the ECM may be irrevocably damaged. Technician B says the computer base scan tool may irrevocably damaged. Who is correct?
Answer B is correct. 1 in. Hg. Is too low; this can indicate a suction side air leak.
38. Fuel filter inlet restriction is being measured on an engine. The specification is 6-10 in. Hg. The test results are 1 in. Hg. Which of the following is indicated? A. The fuel filter is restricted. B. There may be a suction side air leak. C. The fuel filter is serviceable. D. There may be a restriction in the fuel cooler.
Answer B is correct. Only technician B is correct. This is a special feeler gauge designed specifically to gauge the clearance on the compression break.
39. Technician a says the injector is been adjusted. Technician B says item #1 is a feeler gauge. Who is correct?
Answer C is correct. A fail camshaft position sensor could cause the engine to die and prevent the engine from restarting, because the electronica control module (ECM) Would not know when to fire the injector.
4. A diesel engine dies going down the road and will not start. Which of the following could be the cause? A. Faulty air inlet heater. B. Faulty glow plug controller. C. Failed camshaft sensor. D. Failed accelerator pedal position sensor (APP).
Answer A is correct. Valve protrusion being lower than specification can result in low compression and hard starting of a diesel engine.
40. Valve protrusion is lower than specification. This could result in: A. Hard starting. B. Increase valve lash. C. Decreased valve stem height. D. Decrease valve spring installed height.
Answer B is correct. Because the fuel system has sufficient pressure, the low power concern could be caused by restricted air filter.
41. An engine with the fuel system shown in the illustration has low power. Fuel pressure is checked on the outlet side of the secondary fuel filter; The results are shown below. Actual 20 P.S.I Specification 18-22 p.S.I Which of the following could be the cause of the low power concern? A. High fuel pressure. B. Restricted air filter. C. Restricted primary fuel filter. D. Restricted secondary fuel filter.
Answer C is correct. Gasoline does not provide proper lubrication. It causes damage very quickly and could seize all injectors.
42. A diesel engine will not start. The technician finds all six injectors are seized. Which of the following could be the cause? A. Incorrect fuel filter. B. Oil in the diesel fuel. C. Gasoline in the diesel fuel. D. Incorrect oil filter.
Answer B is correct. Only Technician B is correct. A viscous damper. Should be heated during inspection to check for leaks
43. Technician A says a rubber-bonded dampener should be heated during inspection. Technician B says a viscous dampener should be heated during inspection who is correct?
Answer D is correct. The filters should be filled using the hand primer pump. Fuel should not be poured in directly into the filter, as this will enable unfiltered fuel to enter the fuel system.
44. A common rail fuel system high pressure pump has been replaced. Which of the following is true? A. The pump must be time to the engine. B. The pump serial number must be programmed into the ECM. C. All in active (history) codes will need to be removed from the engine to start. D. The fuel filter should be installed and filled using the hand pump primer.
Answer A is correct. If the coolant surges as soon as the engine starts, it is an indication of combustion chamber gas is entering the coolant system.
45. Coolant is surging into the coolant system recovery tank as soon as the engine is started. Which of the following is most likely the cause? A. Blown head gasket. B. Excessive water pump pressure. C. Excessive radiator cap sealing pressure. D. Restricted radiator.
Answer A is correct. A leaking injector tube can allow diesel fuel to pass into the coolant. This condition will often cause the coolant recovery bottle to overflow.
46. The coolant in a diesel engine smells like diesel fuel. This could be caused by A. Leaking injector tube. B. Leaking and take manifold. C. Restricted coolant D. Restricted air filter.
Answer C is correct. Both technicians are correct low transfer pump pressure and volume can cause the injector pump to overheat and fail. After market performance programmers deliver more fuel to the engine, resulting in insufficient fuel in the injection pump for lubrication and cooling.
47. A diesel engine equipped with a PLN-E system has had repeated injection pump failures. Technician A says the transfer left pump should be checked. Technician B says the vehicle should be checked for aftermarket modifications. Who is correct?
Answer D is correct. A restricted oil supply line could prevent sufficient lubrication from reaching the turbo charger bearing and result and turbo charger shaft locking.
48. A new truck has had two turbo charger failures. The shaft lock up on both of them in the last 3,000 miles. Which of the following could be the cause? A. Restricted oil drain. B. Incorrect transmission ratio. C. Incorrect drivetrain ratio. D. Restricted oil supply.
Answer B is correct. Only technician B is correct. The failure mode identifier tells what type of failure has occurred, such as open, short, data out of range, etc.
49. Technician A says a failure mode identifier (FMI) tells what sensor or system the fault is in. Technician B says a FMI tells what type of failure has occurred in the given sensor or circuit.
Answer A is correct. A loose oil filter cap will cost low crank case pressure.
5. All of the following can cause high crank case pressure except: A. Loose oil filler cap. B. Dirty crank case filter. C. Worn rings. D. Damaged air compressor.
Answer C is correct. And incorrect head gasket can cause lower than normal compression, compression, Horse power may or may not be greatly affected.
50. A freshly overhaul diesel engine is hard to start when cold and blows white smoke until fully warmed. Otherwise the engine seems to run OK. Which of the following could be the cause? A. Restricted exhaust. B. Restricted intake. C. Incorrect head gasket. D. Incorrect valve seals.
Answer B is correct. Air bubbles flowing in the return fuel line indicates suction side leaks.
51. There are air bubbles flowing in the return fuel flow. Which of the following is most likely the cause? A. Leaks in the return fuel line. B. Leaks in the suction side fuel line. C. Restricted fuel filter. D. Restricted fuel card.
Answer C is correct. Both technicians are correct. On many models, the actuator will need to be run through and insulation test so that the ECM learns the new actuator position. Many models of actuators are cooled with engine coolant, and it may be necessary to drain the coolant below the level of the actuator prior to removal.
52. The variable geometry turbo actuator has a faulty motor and needs to be replaced technician A says the new actuator may need to be initiated With a scan tool after installation. Technician B says the coolant may need to be drained during actuator replacement. Who is correct?.
Answer A is correct. A piece of cardboard moved around the Suspected leak area with the engine running will safely show the technician the source of the leak.
53. Which of the following would be the best tool to use to help find a high pressure fuel line leak on a diesel engine? A. A piece of cardboard. B. The technicians hand. C. A black light. D. Dryer tracer.
Answer C is correct. The leak is occurring when the engine is cold; Therefore, the test should be performed when the engine is cold. A coolant loss on a cold engine is most likely caused by loose or incorrectly installed post clamps.
54. Every morning, the coolant is low on a truck. However, if the level is brought up to normal, the truck runs all day without any problems or coolant loss. Which of the following should the technician do? A. Check The cool and freeze protection with a refractometer. B. Check the diesel exhaust fluid with a refractometer. C. Pressure test the cooling system with the engine cold. D. Check the SCA additive level.
Answer C is correct. 10 inches of restriction is a normal reading. The air filter should be left alone.
55. A technician finds the air restriction indicator shows 10 inches of restriction. Which following should be done? A. Cleaning the air filter with water and blow dry with low air pressure. B. Clean the air filter with soapy water and blow dry. C. Nothing. D. Replace the air filter.
Answer A is correct. The charge air cooler needs to be replaced, as the danger of pieces of the turbo will being trapped in the charge air cooler and later coming loose and entering the engine is very high.
6. After replacing a turbo charger due to an exploded compressor will, what should the technician do? A. Replace the charge air cooler. B. Clean the charge air cooler. C. Replace the turbo drain line. D. Replace the turbo oil feedline.
Answer B is correct. Only technician B is correct. Engine over speeding can cause the valves to stay open too long ( float) and hit the piston.
7. The valves in a diesel engine have hit the piston. Technician A says this could have been caused by excess of idling. Technician B says this could have been caused by the engine over speeding. Who is correct?
Answer B is correct. 0.72 Volts indicates a high resistance circuit and access voltage drop.
8. A technician is checking voltage drop on the battery cables. Which of the following indicates excess of voltage drop? A. 0.07 volts. B. 0.72 volts. C. 0.20 volts. D. 0.05 volts.
