Question 1

What is the function of an injector leak-off line?

Accepted Answer

A)   vents fuel to atmosphere
B)   prevents fuel leakage into oil
C)   returns fuel to fuel tank
D)   routes fuel to injector pressure chamber C

Question 2

When considering standard EHI operation in a typical CR diesel fuel system, what happens the instant the actuator is energized?

Accepted Answer

A)   pressure builds in the upper (control)  pressure field
B)   pressure collapses in the upper (control)  pressure field
C)   pressure builds in the lower pressure field
D)   pressure collapses in the lower pressure field B

Question 3

Which of the following explains why piezo actuators respond faster to injector driver signals than equivalent solenoid actuators?

Accepted Answer

A)   lighter in weight
B)   mechanical movement takes place without having to build a magnetic field
C)   they use data bus driven signals
D)   respond to wireless driver inputs B

Question 4

When testing forward leakage on a multi-orifice hydraulic injector nozzle, which of the following is an indication of a good nozzle?

Accepted Answer

A)   zero leakage at nozzle orifices
B)   minimal leakage at nozzle body
C)   drop off leakage is less than 150 psi
D)   drop off leakage is less than half NOP

Question 5

When adjusting a high spring type injector nozzle NOP, what should be done to decrease opening pressure?

Accepted Answer

A)   subtract shims
B)   add shims
C)   turn adjusting screw CCW
D)   turn adjusting screw CW

Question 6

What is the main reason VCO nozzle geometry has become common today?

Accepted Answer

A)   lower manufacturing costs
B)   lower HC emissions
C)   lower NOx emissions
D)   easier to recondition

Question 7

What is the main advantage of a low spring design over a high spring type in a typical multi-orifice injector assembly?

Accepted Answer

A)   ease of setting NOP
B)   mass of moving parts is reduced
C)   lower maintenance costs
D)   improved emissions

Question 8

Which of the following types of injector are most vulnerable to damage when removing them for the engine cylinder head?

Accepted Answer

A)   poppet nozzles
B)   flanged multi-orifii
C)   electrohydraulic injectors
D)   pencil nozzles

Question 9

When a pintle type nozzle is found on a current diesel engine system, which of the following would correctly describe its function?

Accepted Answer

A)   DPF dosing injector
B)   common rail fuel injector
C)   secondary injector
D)   pilot injector

Question 10

Technician A says that electrohydraulic nozzles are used with late generation electronic unit injectors (EUIs). Technician B says that EHIs are used with diesel common rail (CR) systems. Who is correct?

Accepted Answer

A)   Technician A only
B)   Technician B only
C)   Both A and B
D)   Neither A nor B

Question 11

Technician A says that EHIs are ECM-controlled but are limited by hard value NOPs. Technician B says that EHIs are used with current common rail (CR) and electronic unit injector (EUI) diesel fuel injection systems. Who is correct?

Accepted Answer

A)   Technician A only
B)   Technician B only
C)   Both A and B
D)   Neither A nor B

Question 12

A slide hammer has been fitted to an injector seized in a cylinder head, but will not pull it. What should be done?

Accepted Answer

A)   drive injector downward into cylinder
B)   heat injector with an oxy-acetylene torch
C)   pull cylinder head, drive injector upward
D)   drill and pull injector with a screw extractor

Question 13

What is another way of saying popping pressure?

Accepted Answer

A)   charging pressure
B)   line pressure
C)   peak pressure
D)   NOP

Question 14

Technician A says that electrohydraulic injectors (EHIs) may use a solenoid actuator. Technician B says that EHIs may use a piezo actuator. Who is correct?

Accepted Answer

A)   Technician A only
B)   Technician B only
C)   Both A and B
D)   Neither A nor B

Question 15

What accounts for the response-delay of EHI nozzles using solenoid actuators compared with those using piezo actuators?

Accepted Answer

A)   solenoids require higher voltage
B)   piezo stacks draw more current
C)   piezo actuators open nozzles without having to move themselves
D)   solenoids must build and collapse magnetic fields before mechanical movement occurs

Question 16

Technician A says that the pressure in a diesel common rail is equal to that the same as that in an EHI when it is closed in a typical CR fuel system. Technician B says that pressures in a diesel CR fuel system are similar to those in a typical gasoline fuel system. Who is correct?

Accepted Answer

A)   Technician A only
B)   Technician B only
C)   Both A and B
D)   Neither A nor B

Question 17

Which of the following components is a requirement with a high spring injector design?

Accepted Answer

A)   double pressure chamber
B)   shims to set NOP
C)   spindle to transmit spring force to nozzle valve
D)   an accumulator chamber

Question 18

When bench testing a multi-orifice hydraulic injector, which of the following values would represent a typical leakoff drop-off specification?

Accepted Answer

A)   two-thirds NOP
B)   150 psi less than NOP
C)   300 psi less than NOP
D)   one-half NOP

Question 19

Which of the following correctly describes atomization?

Accepted Answer

A)   change of state from liquid to gas
B)   change of state from gas to liquid
C)   condensation of a gas to a liquid
D)   reduction of a liquid to minute droplets

Question 20

In a typical multi-orifice, hydraulic injector, what force holds the nozzle valve on its seat?

Accepted Answer

A)   spring force
B)   fuel pressure
C)   combustion pressures
D)   compression pressures

Exam 21: Injector Nozzles

What is the function of an injector leak-off line?

When considering standard EHI operation in a typical CR diesel fuel system, what happens the instant the actuator is energized?

Which of the following explains why piezo actuators respond faster to injector driver signals than equivalent solenoid actuators?

When testing forward leakage on a multi-orifice hydraulic injector nozzle, which of the following is an indication of a good nozzle?

When adjusting a high spring type injector nozzle NOP, what should be done to decrease opening pressure?

What is the main reason VCO nozzle geometry has become common today?

What is the main advantage of a low spring design over a high spring type in a typical multi-orifice injector assembly?

Which of the following types of injector are most vulnerable to damage when removing them for the engine cylinder head?

When a pintle type nozzle is found on a current diesel engine system, which of the following would correctly describe its function?

Technician A says that electrohydraulic nozzles are used with late generation electronic unit injectors (EUIs) . Technician B says that EHIs are used with diesel common rail (CR) systems. Who is correct?

Technician A says that EHIs are ECM-controlled but are limited by hard value NOPs. Technician B says that EHIs are used with current common rail (CR) and electronic unit injector (EUI) diesel fuel injection systems. Who is correct?

A slide hammer has been fitted to an injector seized in a cylinder head, but will not pull it. What should be done?

What is another way of saying popping pressure?

Technician A says that electrohydraulic injectors (EHIs) may use a solenoid actuator. Technician B says that EHIs may use a piezo actuator. Who is correct?

What accounts for the response-delay of EHI nozzles using solenoid actuators compared with those using piezo actuators?

Technician A says that the pressure in a diesel common rail is equal to that the same as that in an EHI when it is closed in a typical CR fuel system. Technician B says that pressures in a diesel CR fuel system are similar to those in a typical gasoline fuel system. Who is correct?

Which of the following components is a requirement with a high spring injector design?

When bench testing a multi-orifice hydraulic injector, which of the following values would represent a typical leakoff drop-off specification?

Which of the following correctly describes atomization?

In a typical multi-orifice, hydraulic injector, what force holds the nozzle valve on its seat?