310T fuel systems Final Exam and All
Correct Answers 2025-2026 Updated.
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 pressure and
timing are controlled by the valves.
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 installation procedures for a EUI, Technician A says that the plunger travel
of the injector is one of the last steps to perform during injector replacement. Technician B says
that the coil resistance and available voltage should be checked after replacing the injector.
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 discussing potential reasons for a hard start and prolonged engine cranking period on a
EUI fuel system, Technician A suggested air could be entering the injectors due to a poorly
seating low-pressure regulator valve. Technician B suggested the complaints are likely caused by
a leaking check valve in a hand primer pump.
, 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 discussing the potential cause of a failed injector with a seized plunger, Technician A says
the failure was likely caused by water in the fuel. Technician B says the cause is likely a worn
plunger and barrel assembly.
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
Correct Answers 2025-2026 Updated.
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 pressure and
timing are controlled by the valves.
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 installation procedures for a EUI, Technician A says that the plunger travel
of the injector is one of the last steps to perform during injector replacement. Technician B says
that the coil resistance and available voltage should be checked after replacing the injector.
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 discussing potential reasons for a hard start and prolonged engine cranking period on a
EUI fuel system, Technician A suggested air could be entering the injectors due to a poorly
seating low-pressure regulator valve. Technician B suggested the complaints are likely caused by
a leaking check valve in a hand primer pump.
, 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 discussing the potential cause of a failed injector with a seized plunger, Technician A says
the failure was likely caused by water in the fuel. Technician B says the cause is likely a worn
plunger and barrel assembly.
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
