Diesel engines EXAM-2

Answer C is correct. Worn valve seats can cause low compression, but will not cause oil consumption. - ANSWER 1. A diesel engine is using too much oil. All of the following could be the cause except: A. Worn piston ring. B. Worn valves guides. C. Worn valves seats. D. Loose oil pan. Answer A is correct. A dial indicator, sometimes known as sled gauge, is normally used to check liner installed Hight. - ANSWER 2. Which of the following would be used to check liner installed height? A. Dial indicator/sled gauge. B. Inside micrometer. C. Outside micrometer. D. Dial caliper. Answer A is correct. A stuck open return check valve can allow fuel to drain back to the tank if the return line is not submerged in fuel. - ANSWER 3. The fuel drains back to the tank after sitting overnight. Which of the following could be the cause? A. A stuck open return check valve. B. A stuck closed return check valve. C. A restricted supply line. D. A restricted return line. Answer C is correct. Both technicians are correct. When replacing a turbo charger, it is a good practice to inspect the oil supply and return lines to ensure proper lubricant flow at the replacement Turbo charger. This can reduce the chances of the replacement turbo failing. Technician B is also correct. Turbo chargers can be recorded; this helps to reduce repair costs. Recording can only be performed if both the turbine and impeller housing are in good condition. - ANSWER 4. In reference to the illustration, technician A says that when replacing a turbo charger assembly, the drain line should be checked for restrictions. Technician B says that turbo chargers are often recorded by replacing the center housing as a unit and reusing the old compressor and turbine housing. Who is correct? Answer B is correct. A stuck Closed thermostat would allow the engine to overheat and the top radiator hose to be cold because the coolant Is not circulating. - ANSWER 5. A diesel engine shows an abnormally high reading on the temperature gage, and the top radiator hose is cold. Which of the following is the most likely cause? A. Stuck open thermostat. B. Stuck closed thermostat. C. Restricted radiator. D. Restricted charge air cooler. Answer A is correct. The regulating valve helps to hold pressure in the low pressure fuel system; if it were stuck open, the fuel pressure would be low. - ANSWER 6. The regulating valve on the fuel injection pump is stuck open. This will result in: A. Low fuel-supply pressure. B. High fuel-supply pressure. C. Engine overheating. D. Lower oil pressure. Answer B is correct. Only technician B is correct. A restricted turbo oil drain line can cause the turbo seals to leak and allow oil to travel into the charge air cooler. - ANSWER 7. A diesel engine that has high oil consumption also has oil in the charge air cooler. Technician A says the air compressor oil drain line may be restricted. Technician B says the turbocharger oil drain line may be restricted. Who is correct? Answer A is correct. Only technician A is correct. A failed boost pressure sensor could cause the electronic control module (ECM) To over fuel the engine, resulting in black smoke. - ANSWER 8. A diesel engine equipped with a common rail fuel system blows excessive 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 C is correct. Milling the cylinder head deck surface will not affect the distance the valve stem protrudes above the cylinder head. - ANSWER 9. All of the following must be checked after a diesel cylinder head has been milled EXCEPT: A. Injector tip protrusion. B. Intake valve head protrusion. C. Valve stem height. D. Exhaust valve head protrusion. Answer C is correct. End-play Is controlled by the clearance between the thrust surface on the crankshaft and the thrust bearing. Excessive crankshaft end-play Is normally caused by excessive wear on the thrust surface of the crankshaft or a one thrust bearing. - ANSWER 10. An engine is being assemble, and the crankshaft end-play is greater than specification. Which of the following could be the cause? A. Crankshaft rod journal is out of round. B. Crankshaft rod journal is tapered. C. Worn crankshaft thrust surface. D. Worn Rear main seal surface. Answer C is correct. Both technicians are correct. Heavy duty fan clutches can be air-applied or air-released. - ANSWER Technician A says some fan clutches found on heavy duty highway trucks are air-applied. Technician B says some fan clutches found on heavy duty highway trucks are air-released. Who is correct? Answer A is correct. A stuck open injector could cause engine over a feeling, producing both a knock and black smoke. - ANSWER 12. A diesel engine has a loud knock accompanied by black smoke. Which of the following could be the cause? A. A stuck open injector. B. A stuck close injector. C. A worn rod bearing. D. A worn main bearing. Answer D is correct. The injector is not adjusted after installation, because high pressure is supplied to the injector, and the injector is open electronically. - ANSWER 13. When installing an injector in an engine equipped with a high-pressure common rail fuel system, which of the following tools is normally used to adjust the injectors? A. Dial indicator. B. Torque wrench. C. High gauge. D. The injector is not adjusted after installation. Answer C is correct. Both technicians are correct. Oil entering the DPF and DOC can cause them to overheat and melt the substrate. - ANSWER 14. Technician A says oil entering the diesel particulate filter (DPF) can damage it. Technician B says oil entering the diesel oxidation converter (DOC) Can cause it to overheat. Who is correct? Answer A is correct. A DDM Set on the Ohms scale can be used to measure the resistance of the coil. - ANSWER 15. Which of the following would be the correct tool to bench test a high-pressure common rail injector? A. Digital multi meter (DMM). B. Test light. C. Fused jumper wire. D. Volt meter. Answer A is correct. A. stuck open thermostat would tend to let the engine run cold. - ANSWER 16. A diesel engine fails to reach operating temperature. Which of the following is the most likely cause? A. Stuck open thermostat. B. Stuck closed thermostat. C. Slipping fan drive belt. D. Slipping fan clutch. Answer C is correct. Both technicians are correct a dynamometer test can be performed to check fueling rates and sensor performance. Also, a check should be made of parameters such as top vehicle speed when the customer has a MPG related concern. - ANSWER 17. A diesel engine has a poor fuel economy concern. Technician A says a dynamometer test could be performed to help verify the concern. Technician B says the customer-adjustable parameters in the ECM should be checked. Who is correct? Answer B is correct. Excessive movement of the camshaft can allow the camshaft to contact the camshaft position sensor. - ANSWER 18. The camshaft of a diesel engine has too much and play. Which of the following could be the result? A. Damage crankshaft position sensor. B. Damage camshaft position sensor. C. Damage injector tips. D. Damage piston cooling nozzle. Answer A is correct. A leaking supply line may allow air in the fuel system and caused this concern. - ANSWER 19. After sitting overnight, a diesel engine will start and then die. It will restart only after priming the fuel system with a hand primer pump. The engine runs fine the rest of the day. Which of the following could be the cause? A. A leak in the supply line. B. A restricted supply line. C. A restricted return line. D. A restricted air filter. Answer C is correct. Both technicians are correct. The injector is controlled by the ECM. An EUI Engine has electronically controlled unit injector for each cylinder - ANSWER 20. Technician A says an EUI engine will have a computer to control the quantity of fuel delivered. Technician B says an EUI engine will have individual electronica unit injectors. Answer D is correct. Excessive wear on both halves of a main bearing is an indication of a bent crankshaft. - ANSWER 21. Which bearing wear pattern would indicate a bent crankshaft? A. Worn lower main bearings. B. Worn up or rod bearings. C. Both halves of the rod bearings are worn excessively. D. Both halves of the main bearings are worn excessively. Answer C is correct. The manufacture must be contacted, as an engine over speeding event can be a warranty voiding event. The manufacturer will track this data in case of future problems. - ANSWER 22. An electronically controlled diesel engine has set a DTC for engine over speeding. What must the technician do to remove the DTC that was set? A. Reflash the ECM. B. Disconnect, then reconnect and unswitched battery power to the ECM. C. Contact the manufacturer for a factory password. D. Press and hold the diagnostic in the dash for 10 seconds. Answer C is correct. Both technicians are correct. When unmetered fuel or oil is allowed to enter the DPF (Caused by a failed turbo charger or failed injector), The chances of melted or plug DPF is high. - ANSWER 23. The DPF pressure sensor has set a code for a restricted catalyst. Technician A says a failed turbocharger can cause this condition. Technician B says a failed injector can cause this condition. Who is correct? Answer A is correct. The jacket water after cooler uses engine coolant to cool the turbo charged air. A crack would allow turbo charger air to enter the cooling system The jacket water after cooler uses engine coolant to cool the turbo charged air. A crack would allow turbo charger air to enter the cooling system. - ANSWER 24. There are bubbles in the cooling system. Which of the following could be the result? A. Crack jacket water after cooler. B. Cracked oil cooler. C. Cracked piston skirt. D. Cracked fuel cooler. Answer B is correct. High resistance in the cables can cause higher than normal voltage drop, because voltage is used to push the current through the resistance. - ANSWER 25. During a starter voltage drop test, voltage drop is higher than specifications. Which of the following could be the cause? A. The engine has low compression. B. The battery cables have high resistance. C. The flywheel ring gear teeth are worn. D. The starter motor has a slipping drive. Answer A is correct. A leaking EGR cooler can allow coolant into the exhaust system. - ANSWER 26. A diesel engine has an internal coolant leak. Which of the following could be the cause? A. Leaking exhaust gas recirculation(EGR)cooler. B. Leaking DPF. C. Leaking DOC. D. Correct fuel cooler. Answer A is correct. Only technician A is correct if the engine brake does not disengage when the clutch is depressed, the clutch switch should be tested. - ANSWER 27. A driver is concerned that the engine brake will not disengage when the clutch is depressed. Technician A says that the clutch switch may be faulty technician B says the master switch may be faulty. Who is correct? Answer A is correct. The radiator cap controls cooling system pressure. A failed radiator cap seal would allow this condition. - ANSWER 28. A diesel engine starts and runs. As the engine warms, coolant runs out of the radiator and into the coolant overflow bottle. Which of the following could be the cause? A. A radiator cap. B. Fan. C. Plug the radiator. D. Over pressurized water pump. Answer C is correct. This reading is abnormally high; It indicates a failure in the fuel pressure sensor circuit. - ANSWER 29. On a diesel engine equipped with a common rail fuel system shown above the fuel rail pressure sensor shows 12,500 p.s.i fuel pressure key on, engine off. Which of the following is true? A. This is normal reading on a cold engine. B. This is normal reading on a hot engine. C. This reading is higher than normal for a key on, engine off. D. This reading indicates the high-pressure pump is malfunctioning. Answer C is correct. Both technicians are correct. Restricted EGR pressure differential sensor tubes can cause the ECM to over EGR the engine, which will reduce the horsepower. A restricted fuel cooler can cause overheated fuel, which will reduce horsepower. - ANSWER 30. A diesel engine has low power. Technician A says the EGR pressure differential sensor tubes may be clogged. Technician B says the fuel cooler may be restricted. Who is correct? Answer A is correct. An over concentration of anti-freeze can cause silicate Drop out and water pump sealto leak. - ANSWER 31. An over concentration of anti-freeze in the cooling system can cause? A. A leaking water pump. B. The engine to run to cool. C. Low power. D. Excessive exhaust temperature. Answer C is correct. A compression break that has been adjusted to lose will cause the break to operate slightly lighter than intended and can cause the compression break to have greater breaking. However, this can also cause valve train damage. - ANSWER 32. In the illustration, adjustment Screw #1 to a clearance 0.002 greater then specified. This would most likely result in: A. An engine that is hard to start. B. An engine that is low on power. C. An engine that has excess of compression braking. An engine that has excess of compression braking. D. Injector damage. Answer A is correct. A plug pick up screen may lack sufficient oil to pass at a lower RPM. when the engine RPM indicates, the increased flow demand may cause the pump to cavitate and pressure to be low. - ANSWER 33. A diesel engine has low oil pressure at high rpm, but oil pressure is normal at lower RPM. Which of the following could be cause? A. Plug pick up screen. B. Dirty oil filter. C. Plug oil bypass valve. D. Restricted oil cooler. Answer A is correct. Only technician A is correct. A leak in the fuel suction system could show up as bubbles in the fuel/water separator. - ANSWER 34. There are air bubbles in the sight glass of the fuel/water separator. Which of the following could be the cause? Technician A says there could be a hole in the suction side hose of the fuel system. Technician B says there could be a hole in the pressure side hose of the fuel system. Who is correct? Answer D is correct. The vehicle must be stationary and park away from any flammable items, because the exhaust system will get hot during this procedure. - ANSWER 35. A technician needs to perform an active DPF regeneration. This procedure should be performed: A. With the vehicle moving. B. With the engine cold. C. With the engine off. D. With the vehicle stationary. Answer C is correct. The refractometer is generally recommended as a most accurate tool for this check. - ANSWER 36. Which tool should be used to check coolant freeze protection on heavy duty diesel engine? A. Ball float gauge. B. Disc float gauge. C. Refractometer. D. Hydro meter. Answer C is correct. This is normal clearance. - ANSWER 37. Which of the following would be the most normal piston to cylinder wall clearance specification for a diesel engine with a 4 inch bore? A. 0.0001"-0.0003" B. 0.001"-0.003" C. 0.008"-0.015" D. 0.100"-0.300" Answer D is correct. Excelerator pedal position is controlled by the driver. - ANSWER 38. The engine temperature sensor input to the computer affects all of the following EXCEPT. A. Fuel quantity. B. Idle speed. C. Injection timing. D. Excelerator pedal position. Answer B is correct. Only technician B is correct. A loose alternator ground could cause high resistance in the negative circuit and caused this amount of voltage drop. - ANSWER 39. A charging circuit has 2 voltage drop on the negative side while under full load. Technician A says this is could be caused by a lose power supply wire at the alternator. Technician B says this could be caused by a loose alternator ground. Who is correct? Answer D is correct. All the components listed can be found in an engine compression break except brake shoes, which would be found on the chassis drum brake system. - ANSWER 40. Which of the following is least likely to be found in an engine compression brake system? A. Master piston. B. Slave piston. C. Solenoid valve. D. Brake shoes. Answer C is correct. Both technicians are correct. Voltage drop on either side of the starter circuit could cause the engine to have slow cranking speed. - ANSWER 41. A diesel engine has a slow cranking speed. Technician A says voltage drop in the battery positive cable could cause this. Technician B says a poor starter ground could cause this. Who is correct? Answer B is correct The negative cable should be removed first to prevent arcing. - ANSWER 42. When replacing the ECM, which of the following should be done first? A. Remove the positive battery cable at the battery. B. Remove the negative battery cable at the battery. C. Disconnect the positive battery cable at the magnetic switch. D. Replace the injectors as they are match to the ECM. Answer C is correct. This is normal charging system output voltage. - ANSWER 43. Normal charging system output voltages: A. 12 volts. B. 12.6 volts. C. 13.5 volts. D. 15.5 volts. Answer C is correct. A defective Starter can draw so much amperage the battery voltage will fail below the minimum for ECM operation and cause the engine to be hard to start. - ANSWER 44. A diesel engine cranks slowly, is hard to start, must sometimes be jumpstarted, and sometimes fail to start. Which of the following is the most likely cause? A. Blown ECM fuse. B. Open j1939 data bus. C. Excessive starter current draw. D. Battery with a high state of charge. Answer D is correct. An ECM with incorrect programming could cause the engine to produce excess of cylinder pressure and result in head gasket failure. - ANSWER 45. A diesel engine in a new truck has a blown head gasket three times in the last 2000 miles which of the following could be the cause? A. Incorrect tire size. B. Incorrect transmission ratio. C. Incorrect differential ratio. D. Incorrect fuel trim settings in the ECM. Answer B is correct. Two little valve lash will Cause the valve to open more than specified. - ANSWER 46. Which of the following would cause a bent valve? A. Too much valve lash. B. Do you little valve lash. C. Too much injector lash. D. Two little injector lash. Answer C is correct. Both technicians are correct. The electrical connector for both the coolant temperature sensor and the fuel temperature sensor typically have two or three wires. - ANSWER 47. Technician A says the coolant temperature sensor will normally have two or three wires in it's electrical connection. Technician B says the fuel temperature sensor will normally have two or three wires in it's electrical connection. Who is correct? Answer A is correct. A feeler gauge is inserted besides the ring to determine Clarence. - ANSWER 48. Piston ring side clearance is measured with a: A. Feeler gauge. B. Dial indicator. C. Outside micrometer. D. Inside micrometer. Answer C is correct. Many engines can be programmed to derate and then shut down due to low coolant level; therefore, A faulty low coolant level sensor could cause this condition. - ANSWER 49. Which of the following could cause a diesel engine to derate and shut down? A. Faulty Excelerator pedal position. B. Faulty turbo boost sensor. C. Faulty low coolant level sensor. D. Faulty biometric pressure sensor. Answer B is correct. The ECM is cooled by the fuel Passing through the plate. - ANSWER 50. The ECM mounting plate has fuel passing through it. Which of the following is true of this design? A. The fuel is cooled by the ECM. B. The ECM is cooled by the fuel. C. The fuel is conditioned by the ECM. D. The ECM is grounded by the fuel. Answer A is correct. He started voltage drop test is performed when the cables are under load. This means it is performed while the engine is cranking. - ANSWER 51. Starter voltage drop test should be: A. While cranking. B. While idling. C. Only on a cold engine. D. Only on a warm engine. Answer C is correct. The line should be removed and inspected. - ANSWER 52. A high-pressure injection line is leaking on a pump line nozzle (PLN) Diesel engine. The line has been torque to specification. Which of the following should the technician do first? A. Replace the line. B. Tight in the line. C. Remove and inspect the line. D. Replace the line and matching fitting. Answer C is correct. Both technicians are correct. Both air in the coolant and low coolant level can cause the coolant temperature probe not to be completely measured in cooling. If the coolant temperature sensor probe is not totally surrounded by coolant, the sensor can give erratic information. - ANSWER 53. Dash mounted temperature gauge is reading erratic. Technician A says air in the coolant can cause this. Technician B says low coolant level could cause this. Who is correct? Answer C is correct. Exhaust valve cool while in the seat. Too little lash would result in too little time in the seat, overheating the exhaust valve. And overheating valve can crack across the valve face. - ANSWER 54. A diesel engine has cracks across the surface of the exhaust valves. Which of the following could cause this? A. Using the wrong oil. B. Using the wrong fuel. C. Two little exhaust valve lash. D. Two little intake valve lash. Answer B is correct. Only technician B is correct a faulty Excelerator pedal position sensor would not affect engine starting, but it would prevent the engine from accelerating. - ANSWER 55. A diesel engine would start, but will only idle. Technician A says a faulty turbo boost sensor could causes this. Technician B says a faulty Excelerator pedal position sensor could cause this. Who is correct?