310T fuel systems|310T engine systems| Ques ons and
answers | Updated RATED A+ | NEW 2025/2026
Technician A says that EUIs are be er than previous injectors because they have no injec on lag
caused by swelling pump lines and delivery valves. Technician B says that the use of
electromagne c solenoids by unit injectors produces injec on delay. Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B
b. Technician B
Technician A says that when se$ng unit injector adjustments during replacement, tune-up, or
overhaul, the proper opera ng clearance should be adjusted using the rocker arm adjus ng
screw. Technician B says that unit injectors do not use opera ng 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
b. Technician B
Technician A says that injec on 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
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
c. Both Technician A and Technician B
Technician A says that an electromagne c solenoid limits the number of injec on events of
most styles of unit injectors to one main injec on. Technician B says that some unit injectors are
capable of having pilot injec on events. Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B
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
a. Technician A
Technician A says that in the latest EUIs, the fuel control valves control injec on ming and
meter the correct quan ty of fuel for injec on. Technician B says that injec on pressure and
ming 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
b. Technician B
While discussing the installa on 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 a5er 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
a. Technician A
While discussing poten al 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
sea ng 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
c. Both Technician A and Technician B
While discussing the poten al 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
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
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 combus on 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
a. Technician A
Technician A says that it is important to use a fuel hand primer to prime an ISX or CELECT fuel
system a5er replacing a fuel filter. Technician B says that a5er installing a dry fuel filter, she
leaves the igni on key on for about 90 seconds to prime the filter before star ng 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
b. Technician B
Technician A says that a CELECT unit injector controls ming and metering by energizing and de-
energizing the injec on control valve during a downward movement of the injector plunger.
Technician B says that the CELECT Plus injector controls metering by energizing the injec on
control valve during downward plunger travel but the injector has a fixed point in plunger travel
which ends injec on.
Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B
d. Neither Technician A nor Technician B
Technician A says that a CELECT injector has two electromagne c solenoids that control ming
and metering events. Technician B says that a single solenoid that is energized at least twice
during a combus on cycle controls ming 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
b. Technician B
answers | Updated RATED A+ | NEW 2025/2026
Technician A says that EUIs are be er than previous injectors because they have no injec on lag
caused by swelling pump lines and delivery valves. Technician B says that the use of
electromagne c solenoids by unit injectors produces injec on delay. Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B
b. Technician B
Technician A says that when se$ng unit injector adjustments during replacement, tune-up, or
overhaul, the proper opera ng clearance should be adjusted using the rocker arm adjus ng
screw. Technician B says that unit injectors do not use opera ng 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
b. Technician B
Technician A says that injec on 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
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
c. Both Technician A and Technician B
Technician A says that an electromagne c solenoid limits the number of injec on events of
most styles of unit injectors to one main injec on. Technician B says that some unit injectors are
capable of having pilot injec on events. Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B
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
a. Technician A
Technician A says that in the latest EUIs, the fuel control valves control injec on ming and
meter the correct quan ty of fuel for injec on. Technician B says that injec on pressure and
ming 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
b. Technician B
While discussing the installa on 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 a5er 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
a. Technician A
While discussing poten al 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
sea ng 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
c. Both Technician A and Technician B
While discussing the poten al 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
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
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 combus on 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
a. Technician A
Technician A says that it is important to use a fuel hand primer to prime an ISX or CELECT fuel
system a5er replacing a fuel filter. Technician B says that a5er installing a dry fuel filter, she
leaves the igni on key on for about 90 seconds to prime the filter before star ng 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
b. Technician B
Technician A says that a CELECT unit injector controls ming and metering by energizing and de-
energizing the injec on control valve during a downward movement of the injector plunger.
Technician B says that the CELECT Plus injector controls metering by energizing the injec on
control valve during downward plunger travel but the injector has a fixed point in plunger travel
which ends injec on.
Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B
d. Neither Technician A nor Technician B
Technician A says that a CELECT injector has two electromagne c solenoids that control ming
and metering events. Technician B says that a single solenoid that is energized at least twice
during a combus on cycle controls ming 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
b. Technician B
