2. Exam 6 additional test questions for practice

Answer D is correct. Blue smoke is an indication of oil consumption. Some causes of blue smoke or worn oil control rings, worn or leaking valve seals, and defective turbo charger seals.

1. All of the following symptoms are indicators of high air inlet restrictions except A. Slow acceleration. B. Low power. C. Collapsing inlet rubber boots. D. Blue smoke.

Answer A is correct. Using a stethoscope, removing the power at each coil or the individual spark plug wires, and performing an electrical cut out tasks using the diagnostic software are all good methods to try and find the engine noise. However, listen to the exhaust to try and determine an engine noise is the least likely method to help a technician discovered the origin of the noise as the exhaust is also very noisy and Wood mask the sound.

10. Which of the following is least likely to provide satisfactory results in attempting to identify an engine noise? A. Listening to the exhaust to determine which cylinder is Causing the noise B. Using a stethoscope. C. Manually disconnecting the power at each coil for quail over plugs or removing the individual spark plug wires. D. Performing and electronica cylinder cut-out test using the diagnostic software.

Answer C is correct. A megnehelic Gage and a water Manometer Are both accurate Tools to diagnose if a paper type air cleaner element needs to be replaced. Most engine manufacturers recommend the element be replaced when the restriction reaches 20 of water column.

11. The most likely method to determine when a paper type air cleaner element needs to be replaced is A. The use of the indicator mounted on the housing of the intake piping. B. Poor engine performance. C. The use of a magnetic gauge or a water Manometer. D. Oil change intervals.

Answer B is correct. A loose we been at the compressor turbine housing will cause low power but will not allow debris to come in contact with the compressor well and is the least likely to cause the condition.

12. A turbo charger is being replaced. The compressor wheel blades are damaged. The least likely cause of this condition is A. Torn air cleaner element. B. Loose of the band at the turbine housing. C. Disconnected air intake hose. D. Miss handling during the installation of the turbo charger.

Answer B is correct. Only technician B is correct. The manufacturer should be contacted with the cylinder serial number so a new label can be a team and permanently attached to the cylinder. This will allow the cylinder to be replaced back into service.

13. During a visual inspection, a fuel cylinder is found to be missing the proper labeling. Technician A says the cylinder needs to be Defueled and condemned. Technician B says the manufacture of the cylinder needs to be contacted with the serial number of the tank to obtain a new label to be installed on the tank. Who is correct?

Answer A is correct. Only technician A is correct. The software will display the intake manifold pressure as absolute, meaning the pressure starts at Atmospheric pressure Plus or minus the sensed pressure once the engine starts. Because NGV engines have throttle valve, at idle the engine will have a vacuum in the manifold. The ECM must be able to determine the condition to be able to regulate the fuel delivery; therefore, absolute pressure is capable of providing both vacuum at idle and pressure once the engine is placed under a load and the turbo charger is providing boost.

14. ANGV engine is been Diagnosed with the diagnostic software. The engine is off with the key switch in the on position. The air intake manifold pressure is displayed as 14.7 psi. Technician A says this is normal condition because the reading is absolute pressure and therefore displays atmospheric pressure plus or minus the manifold pressure. Technician B says the intake manifold pressure sensor is defective because the gauge should be displaying the pressure as 0 until the engine starts to run. Who is correct?

Answer C is correct. Both technicians are correct. The CAC should be clean out with compressed air in the engine and filters should be replaced to ensure that no cooling or metal particles remain in the lubrication system of the engine. Coolant can cause engine damage from the lack of lubrication to the bearings. The filters should also be replaced at the same time because coolant could be trapped inside them, and when the engine is started the coolant would get pushed through the engine.

15. A center called turbo charger has catastrophically fail damaging the cooling portion allowing the cool aunt to leak out. Technician A says the CAC needs to be cleaned out to ensure that no oil or coolant is left inside that could damage the engine when it is restarted. Technician B says the Engine oil and the filters should be replaced to remove as much of the cool aunt or material particles as possible from the engines lubricating system. Who is correct?

Answer C is correct. Both technicians are correct. Technician A is correct because Warren engine lube pump's can cause low oil pressure. Technician B is also correct because CNG engine oil pumps are positive displacement gear type pumps.

16. Technician A says that a worn CNG engine lube pumps may cause low oil pressure. Technician B says that CNG engine oil pumps are positive displacement design. Who is correct?

Answer B is correct. Only technician B is correct. The fuel filters used in CNG systems are a coalescing Type to remove any oil and contaminants that could damage engine sensors or control valves.

17. Technician A says that fuel filters used in CNG systems are made of plated paper to remove oil and contaminants that could damage engine sensors or control valves. Technician B says the fuel filter is used and CNG systems are a coalescing Tight to remove any oil and contaminants that could damage engine sensors or control valves. Who is correct?

Answer D is correct. Neither technician is correct. A mercaptan odor signifies a fuel leak. The leak must be detected and repaired. Suspect areas are the sherex fuel port, fuel lines, and fittings. Pressure relief relief devices should be tested for possible leakage due to eutectic creep. No attempt should be made to introduce any material into the fuel system other than CNG. Dice good coat sensors and render them in effective due to contamination. And electric messing leak detector and/or a soapy water solution or commercially available testing solutions such as snoop are the only approval leak detection devices.

18. And NGV is brought to the shop. In order of mercaptan is detected. Technician A says the odor is normal after refueling technician B says a special die can be added to the fuel to detect the leak As used for the HVAC system. Who is correct?

Answer C is correct. Both technicians 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 and oil or other fluids, Which could cause a hydraulic lock. On in-line multicylinder head, Separate head must be aligned with a straight edge across the intake manifold faces before torquing.

19. Technician A says to use a straight edge across exhaust manifold surfaces to align separate cylinder heads on the engine block. Technician B says to Blow out Head bolt holes to remove any foreign material and to ensure the bolts do not bottom out prematurely and cause improper clamping of the components. Who is correct?

Answer A is correct. Only technician A is correct. I crank case pressure can be caused by a clog crank case breather. It is extremely important that the filter element be serviced on a regular schedule to prevent oil from being carried over from the crank case into the air intake of the engine because eventually the oil will coat the services of critical engine sensor's.

2. Technician A says that excessive crank pressure can be caused from a plug crank case breather. Technician B says that all CNG engines use EGR to control emissions and will have high crank case pressure due to the higher combustion chamber pressure causing more gases to pass by the compression rings. Who is correct?

Answer C is correct. Low-voltage, short in the wiring to the transducer, and a defective transducer will All cars in accurate readings in and electrical oil pressure gauge however, oil pressure in itself would not cause and in accurate reading at the gauge. Of all the engine monitoring devices used on an engine, the oil pressure sensor is one of the most critical.

20. On a vehicle with a electrical oil pressure gauge, all of the following will cause in accurate 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.

Answer C is correct. Both technicians are correct. The CNG engine spark plug external ceramic should be clean with alcohol and a clean towel and should not be touched prior to installation. Contamination from skin oil can cause the spark to jump past the boots and down the ceramic to Ground and caused a misfire when the engine is under load. The boots, prelubricated with dielectric compound from the manufacture and no additional application is necessary.

21. Dielectric compounds are being discussed. Technician A says the external ceramic of spark plugs of CNG engine should be cleaned with isopropyl alcohol and a clean towel before being installed in the engine. Technician B says the CNG engine Sparklett boots come Prelubricated from the factory and are ready to be installed from the container. Who is correct?

Answer B is correct. The description perfectly describes what is often called bottom and knock, which is caused by a failed connecting rod bearing at the big end Or at the crankshaft end.

22. And engine produces a deep sounding thumping noise that is especially noticeable at slow RPM and high engine loads. The most likely cause is A. A knock caused by worn crankshaft main bearings. B. A bottom and not caused by a field rod big end journal. C. A not caused by a warrant crankshaft bearing. D. A not caused by a defective valve rocker arm.

Answer C is correct. Both technicians are correct. Cylinder hydraulic block is usually caused by liquid, usually engine coolant, feeling the cylinder above the piston, prevents the engine from rotating. A crack in a cylinder head or a Cylinder liner is possible source of coolant that could fill a cylinder.

23. A recently overhauled engine suddenly develop cylinder hydraulic block. After cleaning the liquid from the cylinder, inspecting the heads, and replacing the head gasket, the problem Reoccurs. Technician A says the cylinder liner could have a pin hole in the piston compression bring traveling area. Technician B says the cylinder head may have a hairline crack. Who is correct?

Answer Answer B is correct. Only technician B is correct. Testing in oil cooler core should be undertaken at a major engine overhaul and would not be part of a routine PMI schedule.

24. Technician A says that testing of the oil cooler core is to done at P.m. intervals. Technician B says that testing of the cooler core is to be done as part of an Engine overhaul. Who is correct?

Answer A is correct. The most likely cause is too large of a gap. This will cause a very high KV, depending on the amount of excess gap and the voltage you needed to jump it.

25. The most likely cause of spark plug having high KV is A. Two large of a gap between the electrodes of the spark plug. B. Tracking on the center electrode of the spark plug. C. A defective ICM. D. A defective coil.

Answer D is correct. Neither technician is correct. If the head is allowed to become too thin, the cylinder head can warp Side to side, transversely as well as lengthwise.

26. Technician A says the cylinder head can be Resurfaced as much as necessary to bring it back into flatness specifications. Technician B says the cylinder head only warped lengthwise, not side to side. Who is correct?

Answer D is correct. Neither technician is correct. Before condemning the starter, the state of charge of the batteries need to be verified with a DVOM while attempting to start the bus. If the batteries cannot maintain a minimum of 9.6 V while cranking, then they need to be replaced with a fully charge set. The starter should be re-check for starting. Both the positive and negative battery cables and connections should be checked for corrosion and looseness. Because the starter try to engage, verified by the clicking sound of the starter solenoid, the logic has been completed and therefore the fuel door switch is sending a ground input to the I/OControls.

27. And NGV transit bus with the Dinex I/O logic controls is Brought to the shop for not cranking. The starter solenoid is hard clicking. Technician E says the starter is the most likely problem and it should be replaced. Technician B says the fuel door should be checked to make sure it is closed and the safety switch is sending the ground input to the I/O logic controls. Who is correct?

Answer D is correct. Neither technician is correct. A crack in the counterbore flange of a wet sleeve requires that it be replaced. Because it is possible for a Wesley flange to crack and not damage the block counterbore, the block counterbore should be carefully measured and inspected and may not need to be re-cut.

28. A small crack is detected in a wet sleeve around the counter bore flange. Technician A says to use heliarc welding To seal the crack. Technician B says the block needs to have the counterbore re-cut. Who is correct?

Answer A is correct. Only technician A is correct. The 12 V is supplied directly from the batteries to the coil's whenever the ignition is on. The ICM will control the ground signal to the coils to enable the coil's to discharge the Hi voltage to the spark plugs

29. A Detroit diesel series 50G CNG Engine coil power is being discussed. Technician A says that 12 V air supply to the coils whenever the ignition is turned on directly from the batteries. Technician B says that 12 old is applied to the coil by the ICM When the coil has to supply the spark voltage to the plugs. Who is correct?

Answer C is correct. Both technicians are correct. With no visible external signs, the engine may have a leaking head gasket. Draining some engine oil from the oil pan will allow determination of whether the head gasket is leaking the coolant because the coolant is heavier than oil and will run out first. A leaking heater core will show up either in the cab or through the A/C drain.

3. A cooling system is pressurized with a pressure tester to locate a coolant leak. After 15 minutes, the test gauge has dropped from 9 to 5 psi, and there are no visible signs of coolant leaks in the engine compartment. Technician a says the engine may have a Leaking head gasket. Technician B says that the heater core may be leaking. Who is correct?

Answer D is correct. Neither technician is correct external or internal gear type oil pumps are positively displacement types of pumps and do not need to be submerged in oil to be able to pump; they only require priming.

30. Technician A says the external gear type engine oil pump have to be submerged in oil to be able to pump oil. Technician B says internal gear type royal palms have to be submerged in oil to be able to pump oil who is correct.

Answer A is correct. Only technician A is correct. Missing connector sales and/or broken locks are the number one reason for corrosion occurring on the pans in sockets of sensors. Because the Lock is broken or missing, the connector is free to back off, exposing the pans to moisture and dirt that allow corrosion to form.

31. Upon inspecting the coolant sensor connector, the technician find the lock and seal are missing. Technician E says the connector assembly must be replaced with a new one. Technician B says installing a new seal and a zip tie to hold it in place is sufficient. Who is correct?

Answer C is correct. Both technicians are correct. Reusable cylinder head bolts have to be inspected to make sure they are not stretched beyond use by using a special bowl gauge. Erosion and petting are conditions that must be detected and corrected prior to reuse in bolts. Stretch to yield bolts are usually replace each time they are removed.

32. Technician A says before installation, some manufacturers require The head bolts to be cleaned and inspected for erosion or padding as well as to their lines. Technician B says that talk to Yo both need to be replaced with new ones because they are not reusable. Who is correct?

Answer C is correct. isopropyl alcohol Is the recommended cleaning agent of the secondary ignition circuit.

33. The most likely material to clean the spark plugs of a CNG engine before installing them is A. Contact cleaner. B. Brake cleaner. C. Isopropyl alcohol. D. Water.

Answer B is correct. Only technician B is correct. Water can be used to vent or purge a CNG fuel cylinder.

34. Technician A says that when venting a cylinder, compressed air should be used. Technician B says that water can be used. Who is correct?

Answer B is correct. Only technician B is correct. The coolant level should be checked and corrected if needed before any repairs are Initiated. If the coolant is low, then the source of the leak should be found and corrected by Pressure testing.

35. And operator comes to the shop with a complaint of a intermittent low coolant signal on the dash. Technician A says the local improv is the defect and should be replaced because when low coolant is sent by the engine, the local in error stays active and will not turn off until the engine is turned off and back on again. Technician B says the coolant level needs to be checked and corrected if needed before making any repairs, and if the coolant is low the cooling system should be pressure tested to determine the problem league.

Answer D is correct. A stumble or miss is indicative of an engine misfire

36. Which of the following exhaust conditions is most likely indication of an engine misfire? A. Blue colored smoke from the tailpipe. B. Excessive rattling of the exhaust system. C. Cold tail pipe exhaust temperatures. D. A stumble or miss from the engine.

Answer C is correct. isopropyl alcohol Will remove all residues from the spark plug as well as the tools and all accessory secondary circuit components.

37. All of the following can cause flashover of the spark plug except A. And excess a spark plug gap. B. A spark plug contaminated with oil residue from a dirty spark plug socket at installation. C. Cleaning the spark plug with isopropyl alcohol Before installation. D. Handling a spark plug with bare hands during gapping and installation.

Answer C is correct. Both technicians are correct. Small popping sounds can result from the liner moving back into position after moving out of piston After the cylinder was Deerfield especially if for any extended period of time liners use in type IV tanks are permeable And can allow trace amounts of methane that and electric leak detector candy tech or a technician can sometimes smell.

38. Type IV Cylinders are being refilled after they were empty to replace the fuel tank shut off solenoid. Technician capital a size small popping sound coming from the cylinders while refueling them is normal because the cylinder is setting back into place. Technician B says it could be possible to detect the smell of mercaptan and for an electronica leak detector to detect trace amounts of methane coming from a type IV Tank because of the Permeable liner used in these tanks. Who is correct

Answer C is correct. Hey stuck waste gate will deliver low power due to the ECM receiving a low turbo boost signal. In return fuel will be reduced to the combustion chamber this will not damage the catalyst

39. All of the following are caused of catalyst contamination except A. Coolant leaking into the combustion chamber. B. Worn oil control rings. C. Stuck open Waze gate. D. Warren exhaust valve guide seals.

Answer A is correct. The display Multiplex and controller communication is most likely faulty.

4. A transit bus is equipped with a logic control drivers display panel. All the lights are erratic including the oil pressure indicator light. The ECM has not turned on the check engine lamp and all of the accessories are still functioning, including the HVAC. Which of the following is most likely the cause? A. A faulty dash multiplexing controller signal. B. A faulty alternator. C. A faulty oil pressure sensor. D. A faulty ECM.

Answer A is correct. Only technician eight is correct. With a CPS installed correctly, the gap will be maintained to the manufacture specification.

40. Crank position sensor (CPS) is being discussed technician A says the sensor is designed so that once inserted into the block, the gap will be automatically set to the manufacture specifications. Technician B says the sensor to target must be measured and the sensor must be a shame to achieve the accurate yet. Who is correct?

Answer D is correct. Because the ITT feel high pressure fuel regulator has a heat exchanger built into it, it is possible for the diaphragm to become defective and allow fuel to migrate into the coolant.

41. The most likely cause of methane in the coolant surge tank is A. Defective 1/4 turn shutoff valve. B. Plug up secondary fuel filter. C. Cracked cylinder head. D. A defective ITT fuel high-pressure fuel regulator.

Answer D is correct. Minimum head deck to deck thickness is critical if a cylinder head is machine below the minimum specifications, it will be much more likely to crack and do two it's now thinner casting. Additionally, when the head becomes thinner, critical valve train geometry angles are changed. The figure indicates the middle of a headache to deck specifications.

42. An NGV engine cranks but will not start. All of the following are possible causes of the no start condition except A. No power to the coils due to a defective power fuse. B. Fuel 1/4 turn valve turned off. C. No crank sensor signal received by the ECM. D. Stuck open turbo charger wastegate.

Answer C is correct. Both technicians are correct. Technician A is correct because if a coil becomes cracked, the insulating material of the coil will no longer be intact, allowing the spark to jump to ground, especially when the spark intensity is very high such as when the engine is under a load. Technician B is also correct. When contamination Such as engine oil which also attracts dirt is allowed to remain in the spark plug well in oil can become a conductor when it is heated to high temperatures. Causing the engine to misfire.

43. AC NG engine is being diagnosed for a misfire complaint. Technician A says the Coil should be checked for cracks that could cause the spark to jump to ground, causing the misfire. Technician B says the coil should be checked for contamination such as engine oil on the outside because that could cause a spark to jump to ground and cause a misfire. Who is correct?

Answer D is correct. Minimum head deck to deck thickness is critical. If a cylinder head is machine below this minimum specific Quetion, it will be much more likely to crack due to its now thinner casting. Additionally, when the head becomes thinner, critical valve train geometry angles are changed. The figure indicates the minimum head deck to deck specifications

44. The cylinder head deck to deck thickness measurements indicate in the figure above is to A. Prevent cylinder head warpage. B. Calculate valve guide height. C. Determine cylinder warpage. D. Determine resurfacing limit. I

Answer B is correct. Only technician B is correct. Due to the increase of torque manipulation in years 1 through 3, 4th gear, which is a 1:1 ratio, Will place the drivetrain under lower torque power demands without leaving the shop. Only with a DDR or Allison doc software can the clutch enable test be performed. Stall testing longer than 30 seconds or maximum converter out fluid temperature of 300°F without a cool down. Of two or three minutes intervals can result in transmission damage due to elevated transmission fluid temperatures.

45. Technician A says That an NGV with an automatic Allison World transmission can never be stall tested, only road tested, or Dino has to be used to simulate a full power condition. Technician B says that an NGV with an automatic Allison World transmission Should only be stalled tested in fourth gear with the DDR or the Alice in DOC software glitch in abled test and no longer than 30 seconds to stimulate a full power condition. Who is correct?

Answer B is Only technician B is correct. The ICM sans up to 300 V to the coil's primary circuit to ensure the coil is capable of having multiple spark discharge (MSD) Daring the power stroke of the engine for Eileen and clean burning cycle.

46. A Cummins I SLG 8.9 engine model is being discussed. Technician E says that the voltage for the primary side of the coil is delivered through and ignition control circuit of the vehicle sores from the batteries. Technician B says that the ICM delivers up to 300 V to the coil's primary circuit. Who is correct?

Answer B is correct. Only technician B is correct. Because the carbon chain is smaller (les carbon content in the fuel) , The CNG engine will not produce black smoke if there is a lack of air as compared with a diesel or gasoline engine.

55. The color of CNG exhaust smoke is being discussed. Technician A says the lack of air in a CNG engine will cause blue smoke. Technician B says that because of the smaller carbon chain of methane, CNG engines probably will not produce black smoke Who is correct?

Answer D is correct. The threat of a spark plug adapter have to be in good condition. If the spark plug does not screw down into the tube easily, the tube should be replaced. Because the spark plug cannot be installed easily, the next time the plug needs to be change it could be very difficult to remove and cause a spark plug adapter to unscrew out of the cylinder head, resulting in extensive labor to repair the problem.

47. All of the following statements about the spark plug adapter tubes are true except A. The adapter tubes have to be free of contamination such as oil or dirt. B. The adapter tubes are cool by coolant surrounding the tube. C. The adapter tubes have O-ring seals to prevent coolant from leaking into the engine oil. D. The adapter to spark plug thread can be lubricated with anti-seize compound if they are not smooth.

Answer B is correct. The least likely to want to be used to check inside diameter of a valve guide would be a feeler gauge.

48. Which of the following is least likely to be used to check the inside diameter of a valve guide? A. Snap gauge. B. Feeler gauge. C. Ball gauge. D. Dial ball gauge.

Answer C is correct. Both technicians are correct and Infared prion meter is a very good tool to identify misfire in cylinder is because exhaust port temperatures are directly connected to the power output of the cylinder. The diagnostic software it will enable the technician to turn off the cylinders one at a time a distinct change and sound will be heard from the cylinder firing normally, whereas week or dead song as well produced no or very little changes in Sal.

49. A CNG engine Appears to be miss firing. Technician A says to use an infrared pyrometer to find the defective cylinder; a cooler cylinder exhaust port usually indicates a misfire in cylinder. Technician B says the diagnostic software should be used to determine which cylinder is not firing by cycling out each cylinder individually and listening for the cylinder worst cancellation result in no distinct change and sound. Who is correct?

Answer B is correct. Oil coolers are heat exchangers consisting of a housing and a bundle through which coolant is pumped and around which oil is circulated. Oil temperature is in CNG engines run higher than coolant temperature is typically around 230° however, the engine coolant reaches its operating temperature more rapidly than the oil and plays a role in heat in the oil to operating temperature in cold weather start up/warm up conditions. The figure shows an oil Cooler.

5. The figure above shows what part of the lubrication system? A. Oil filter. B. Oil cooler. C. Filter housing. D Oil pump.

Answer A is correct. Only technician A is correct. A good spark plug that is properly gap will generally require between 5 and 20 KV to jump the gap, depending on the cylinder pressure and the amount of fuel in the chamber. When the voltage starts to exceed 25 KV, the spark plug tends to start to misfire when the engine is on your maximum load.

50. A CNG engine is being discussed. Technician E says the voltage required to jump the spark plug gap ranges from five KV to as high as 20 KV. Technician B says the voltage required to jump the spark plug gap is generally around 40 KV. Who is correct?

Answer C is correct. Both technicians are correct. Technician A is correct. A cylinder block suspended to be cracked can be immersed in hot water for up to two hours when pressure testing. This time period should be sufficient to swell any cracks and to be able to observe to a leak. Technician B is also correct. CNG engine manufacturers recommend that a cracked cylinder block be replaced red rather than repair

51. When air pressure testing an engine block, technician E says the block needs to be submerged in hot water for about two hours and then the water check for bubbles. Technician B says cracked cylinder block should be replaced. Who is correct?

Answer A is correct. Only technician A is correct in his description of how manufacturers want cylinder head bolts torqued

52. Technician A says cylinder heads are always tour and sequence according to specifications set by the manufacture. Technician B says that any push rod that are bent must be straight in. Who is correct?

Answer B is correct. In the figure, but dial indicator located to check turbine shaft and play.

53. In the figure above, the technician is checking the turbo charger for A. Radio round out. B. Turbine chef and play. C. Turbine fin wear. D. Compressor fin wear.

Answer D is correct. The electrodes are eroded. The most likely condition is where through normal usage over a period of life of the spark plug.

54. The most likely condition of the spark plug electrode picture above is A. Overheated. B. Improperly gap. C. Contaminated with deposits. D. Worn through normal use.

Answer D is correct. The ITT fuel pressure regulator Is the least likely item to log a DTC for a low fuel pressure. All of the above items should be checked first to ensure they are functioning correctly before fall team the high pressure regulator.

56. The least likely causes of a low fuel pressure DTC being logged when the engine is under a load is A. Lack of coolant flow through the heat exchanger of the ITT fuel pressure regulator. B. Fuel pressure sensor that has drifted to the low side. C. A restricted fuel filter due to contamination. D. A defective fuel high pressure regulator.

Answer A is correct. Message Jess and valves can open at the correct timing or not at all, causing the cylinder to misfire.

57. A misfire in cylinder is diagnosed on a CNG engine to a specific cylinder. The technician replaces the spark plug on the misfire in cylinder. However, the engine continues to misfire. Which of these could be the cause? A. Miss adjusted valves on a cylinder. B. A clog secondary fuel filter. C. Low fuel delivery pressure. D. A boost pressure leak in the air intake piping.

Answer D is correct. The 20 Sean is designed to cut a cylinder liner counterbore. Check the cylinder sleep counterbore for the correct debt and circumference. Counterbore dip shit typically not very buy more than 0.001. Counterbore death can be subtracted from the sleeve flange dimensions to calculate sleeve protrusion. The counterbore should be re-cut using the OEM recommended Tools and specifications.

58. What task is being performed in the figure above? A. Removing the liner carbon ridge. B. Removing the cylinder liner. C. Machining the liner crosshatch pattern. D Cutting the liner counterbore.

Answer B is correct. Weld tubing is not utilize for high-pressure CNG fuel Lyons because of strength requirements and the world bead can lead to leaks.

59. All of the following are true of high-pressure fuel lines except. A. Usually manufacture using stainless steel material. B. Manufactured from welded tubing. C. Must be tampered. D. Minimum wall thickness requirements four different diameters

Answer C is correct. Both technicians are correct. And indicator lamp can burn out or be unplugged to mass a defect. Because of the unknown buzzer and a drivability issue, a DTC should be suspected as having been logged. Whenever the ignition is energized , Hey self checking of the bulbs of The bulbs for five seconds is initialized and then lights turn off. If an active DTC exist, then the indicator will turn back on if the bulb is functioning. The Dd are in diagnostic software allows a technician to energize the CEL or SEL indicators to check them.

6. A customer brings a vehicle that has drivability issues. There are no indicator lights on the dash but the operator complains of a warning buzzer. Technician A says that the ignition switch should be switched off and turn back on while observing the CEL and SEL Indicators to ensure they work. Technician B says the DDR or a diagnostic software will allow the technician to power up the CELNSEL indicators through the ECM to test them. Who is correct?

Answer D is correct. Neither technician is correct. The engine run switch is usually attached to the cover if a metal cover is fabricated and installed it could cause the switch to ground out and cause the engine to stall that could cause an unsafe condition. The manufactures design should not be altered. Duct tape is useful but can fall off or become dislodged, allowing dirt and moisture to enter the rear run box. The correct cover should be installed and secured after cleaning and Drying out the box.

60. An NGV Is being inspected in the shop. The rear apparatus box cover is cracked and a piece of it is missing. Technician A says the cover should be replace with a metal cover because the plastic one is too weak and will fail again. Technician B says a piece of duct tape can be applied to the cracks and seal up the missing piece. Who is correct?

Answer B is correct. The probable source of soot-type Material in the intake manifold of a turbo charged, air cooled CNG engine is the air intake piping is probably defective and allowing light dirt to pass through into the manifold. Soot-type Material in the intake manifold is not normal in most CNG engines.

7. On a CNG engine with charge air cooler, the technician noticed a soot-type Material in the intake manifold. What should the technician check first? A. CAC. B. Air intake piping. C. Intake manifold. D. Head gasket.

Answer D is correct. Neither technician is correct. The IAT sensor sensor is the temperature of the air as it passes through the intake manifold and transmit the information to the ECM and the ECM Command the engine fan to turn on forcing cooler air pass The fans of CAC removing heat from the boosted air inside. There is no coolant passing through the CAC.

8. Technician A says the ECM does not have any control over the temperature of the air as it passes through CAC of an electron a control CNG Engine, technician B says the cool aunt is what caused the air passing through the CAC.

Answer B is correct. Only technician B is correct. Oil leaks can be found by adding a die to the engine oil that is visible under ultraviolet light.

9. Technician A says oil leaks are always caused by gasket material figure. Technician B says that oil leaks can sometimes be located by adding a dye to engine oil that is visible under ultraviolet light. who is correct?