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310 T FUEL SYSTEMS EXAM QUESTIONS AND CORRECT ANSWERS
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Technician A says that EUIs are better than previous injectors because they have no injection lag caused by swelling pump lines and delivery valves. Technician B says that the use of electromagnetic solenoids by unit injectors produces injection delay. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that when setting unit injector adjustments during replacement, tune-up, or overhaul, the proper operating clearance should be adjusted using the rocker arm adjusting screw. Technician B says that unit injectors do not use operating clearances and only injector preload is set on the injector's adjuster spring. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that injection spray-in pressure from a unit injector can change with engine speed. Technician B says spray-in pressures depend only on a EUI's nozzle opening pressure. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B
d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that the electrical signal to a EUI injector is pulse-width modulated (PWM), but unlike other PWM signals it does not have a duty cycle. Technician B says the electrical signal is DC current. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER c. Both Technician A and Technician B
Technician A says that an electromagnetic solenoid limits the number of injection events of most styles of unit injectors to one main injection. Technician B says that some unit injectors are capable of having pilot injection events. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER c. Both Technician A and Technician B
Technician A says that secondary filters used by EUI fuel systems filter down to 2 microns. Technician B says that secondary fuel filters used by EUI fuel systems filter 10-20 microns. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that in the latest EUIs, the fuel control valves control injection timing and meter the correct quantity of fuel for injection. Technician B says that injection
Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that a Cummins diesel engine installed in an automobile won the Indianapolis 500 race one year. Technician B says that diesels are too slow to even qualify for a race. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that Cummins ISX injectors do not use a nozzle valves. Technician B says that all injectors need a nozzle valve to control fuel spray-in pressures and prevent combustion gases from entering the fuel system. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that it is important to use a fuel hand primer to prime an ISX or CELECT fuel system after replacing a fuel filter. Technician B says that after installing a dry fuel filter, she leaves the ignition key on for about 90 seconds to prime the filter before starting the engine. Who is correct? a. Technician A
b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that a CELECT unit injector controls timing and metering by energizing and de-energizing the injection control valve during a downward movement of the injector plunger. Technician B says that the CELECT Plus injector controls metering by energizing the injection control valve during downward plunger travel but the injector has a fixed point in plunger travel which ends injection. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER d. Neither Technician A nor Technician B
Technician A says that a CELECT injector has two electromagnetic solenoids that control timing and metering events. Technician B says that a single solenoid that is energized at least twice during a combustion cycle controls timing and metering in a CELECT system. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that an HPI-TPI fuel system uses a single timing solenoid to control fuel pressure to three injectors. Technician B says that a single metering solenoid controls fuel pressure to three injectors. Who is correct? a. Technician A
d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that both the CELECT and HPI-TPI injectors are adjusted by bottoming out the injector plungers when the injector lobe is on its outer base circle. Technician B says that both injectors are adjusted when the injector lobe is on its outer base circle and when the engine is positioned approximately 45 degrees after TDC. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that higher levels of detergents and antifriction additives are needed by HEUI engines to maintain stable injection control oil pressure. Technician B says that antifoaming agents are more important for a smooth and efficient engine operation. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says amplified wave attenuation (AWA) fittings in the oil manifold of some G2 HEUI engines reduce irregular combustion noise. Technician B says split shot injection reduces combustion noise. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER c. Both Technician A and Technician B
Technician A says an above-normal increase in the duty cycle of the PWM signal applied to the HEUI ICPR of a Cat C7 engine indicates the engine oil has thickened due to excessive soot loading. Technician B says a jumper plug in the wiring harness indicates to the engine's ECM that 10w-30 engine oil rather than 15w-40 oil is being used in the crankcase. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER d. Neither Technician A nor Technician B
Technician A says the measuring unit for the electrical signal to the injection control pressure regulator of a HEUI fuel system is reported as a percentage (%) on a scanner display of engine parameters. Technician B says the PWM signal is reported as time (in milliseconds). Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
While diagnosing the cause of a hard start/prolonged cranking complaint, Technician A says that the high-pressure oil between the high-pressure pump and injectors should stay pressurized for days. Technician B says the oil pressure to the injectors should quickly drop to zero when the engine is shut off. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B
While discussing the purpose of pilot or split shot injection, Technician A says HEUI injectors use it to reduce NOx emissions. Technician B says PRIME metering is used to reduce combustion noise. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER c. Both Technician A and Technician B
While considering ways to increase engine power output, Technician A says that using a special injection control pressure (ICP) sensor, which reports oil pressure as lower than the actual pressure, is an effective shortcut. Technician B says that using the modified ICP sensor signal will result in less fuel injected. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER d. Neither Technician A nor Technician B
Technician A says that a common rail engine can vary the injection pressure, timing, and injection rate shape for each injector. Technician B says that the injection pressure is the same for all injectors in common rail engines, and injectors can perform multiple injection events during each combustion cycle. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
Technician A says that servo injector actuators use a small amount of control valve movement to control larger, more powerful, and faster-acting hydraulic forces. Technician B says that control valves that use piezoelectric control valves are the only actuators capable of servo action. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that rate shaping involves changing the amount of fuel discharged from the injector spray holes. Technician B says that rate shaping requires multiple injection events and a high-pressure fuel system with the ability to vary injection pressure. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER c. Both Technician A and Technician B
Technician A says that dirt bypassing the filter on many common rail injectors can cause an injector to stick open and continuously fuel a cylinder. Technician B says that any dirt particles may potentially damage the injector, but would not allow an injector to full fuel or the engine to run away. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
Technician A says that cylinder misfires can be detected on common rail engines by slightly cracking open the fuel line to each injector when the engine is running. Technician B says that it is important to place a shop towel over the injector when checking for misfires to prevent pressurized fuel from penetrating the skin. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER d. Neither Technician A nor Technician B
Technician A says that Detroit ACR injectors will amplify injection pressure under heavy loads as needed by the engine. Technician B says that injection amplification in the ACR injector takes place at engine speeds just above idle. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER b. Technician B
While discussing the purpose of a second electrical control valve, which regulates fuel volume supplied to the inlet of the high-pressure pump, Technician A says the volume control valve helps improve fuel economy. Technician B says the volume control valve is needed to reduce emissions. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER a. Technician A
While performing a back-leakage test for a first-generation Bosch common rail fuel
system, the fuel volume was measured to be above specification. Technician A says the cause could be a leaking quill tube. Technician B says the cause could be one or more injectors with worn-out ball valve seats. Who is correct? a. Technician A b. Technician B c. Both Technician A and Technician B d. Neither Technician A nor Technician B - ANSWER c. Both Technician A and Technician B
How many solenoids does a Delphi E3 injector have? a) None b) Two c) One d) Three - ANSWER b) Two
Which of the following EUI components is most quickly damaged by abrasives in fuel? a) The spill control valve b) The stator c) The injector plunger d) The nozzle valve - ANSWER a) The spill control valve
Which of the following conditions is likely caused by an unusually long injector response time in a unit injector? a) Resistance in the solenoid circuit b) Voltage to the injector that is too high c) Injectors that are cold d) Incorrectly adjusted injector plunger travel - ANSWER a) Resistance in the solenoid circuit
In an early EUI injector, what happens as engine rpm increases and injector pulse width remains the same? a) Delivery quantity stays the same b) Delivery quantity decreases c) Injection timing advances d) Delivery quantity increases - ANSWER d) Delivery quantity increases
Which of the following conditions will most likely cause diesel fuel to enter the engine coolant of an electronic unit injected engine? a) Corroded injector cups b) Corroded copper sealing washers on injector tips c) Leaking injector jumper tubes d) Leaking injector O-rings - ANSWER a) Corroded injector cups
What fault code is produced from an HD-OBD-compliant engine if there is a broken wire on an injector terminal of an EUI on cylinder 3? a) 651- b) 653- c) 651- d) 651-6 - ANSWER b) 653-
Delphi E3 EUIs are capable of injection pressures of ____________ psi. a) 35,000-38, b) 38,000-41, c) 20,000-25, d) 25,000-30,000 - ANSWER a) 35,000-38,
Early EUI designs started and ended fuel injection through ____________.
a) de-energizing E.C.M. b) changing fuel charging pressure c) EUI spring return force d) SCV operation - ANSWER d) SCV operation
Current ramping is also described as ____________. a) peak and hold b) inductive resistance c) PWM d) hold and drop - ANSWER a) peak and hold
When would a current low fault code be logged? a) Failed ECM b) Shorted injector c) Grounded wiring d) Disconnected injector wiring - ANSWER d) Disconnected injector wiring
Caterpillar ET will indicate injector solenoid status during testing as ____________. a) OK b) Open c) Short d) All of the above - ANSWER d) All of the above
Water trapped within an EUI can ____________. a) seize the injector b) cause injector tip failures c) cause premature wear
pressure from the fuel pump decreases, which of the following will take place? a) More fuel will enter the injector b) Engine power output will increase c) The time available to fill the injector with fuel will increase d) The engine's torque output will drop - ANSWER d) The engine's torque output will drop
Consider a Cummins CELECT injector. Which of the following takes place when the injection control valve is open longer during the downward stroke of the plunger? a) Delivery quantity increases b) Delivery quantity decreases c) Injection timing retards d) Injection timing advances - ANSWER c) Injection timing retards
The beginning of injection in an HPI-TPI Cummins engine is controlled by: a) injector plunger height. b) a PWM electrical signal to the injector solenoid. c) a PWM signal to the electronic fuel control valve. d) fuel pressure in one of the fuel rails to the injectors. - ANSWER d) fuel pressure in one of the fuel rails to the injectors.
HPI-TPI fuel injectors are: a) hydraulically actuated. b) open nozzle. c) common rail. d) closed nozzle. - ANSWER b) open nozzle.
How many solenoids are integrated into the Cummins HPI-TPI injector?
a) None b) Four c) One d) Two - ANSWER a) None
The fuel pressure in a Cummins ISX fuel filter is: a) closest to 90 psi (6 bar). b) always at a negative pressure when the engine is running. c) closest to 380 psi (26 bar). d) closest to 250 psi (17 bar). - ANSWER d) closest to 250 psi (17 bar).
How many timing actuators are required for the front three cylinders of an ISX HPI-TPI fuel system? a) None b) 2 c) 3 d) 1 - ANSWER d) 1
The force used to pressurize fuel for injection in an ISX fuel system is supplied by: a) the metering actuator. b) a radial piston fuel pump. c) an engine-driven gear pump. d) an engine-mounted camshaft. - ANSWER d) an engine-mounted camshaft.
Consider the ISX HPI-TPI injector. Increasing fuel pressure supplied to the timing plunger will: a) retard injection timing. b) advance timing and increase injection quantity.
