Question 1

How is the piezo stack in a EHI linked to the control valve?

Accepted Answer

A)   Directly with a piston.
B)   By a fuel-charged hydraulic coupler.
C)   By the injector spindle.
D)   Using a fuel charged duct.

Question 2

What determines the injectors nozzle opening pressure (NOP)  in a hydraulic injector?

Accepted Answer

A)   It is a soft value controlled by the PCM.
B)   Injector spring tension.
C)   Injector actuators.
D)   Fuel pressure.

Question 3

What is the practice of dividing an injection pulse into several injection pulses during a single intake cycle referred to as?

Accepted Answer

A)   Variable-pulse injection.
B)   Multi-phase injection.
C)   Multi-pulse injection.
D)   Delayed-phase injection.

Question 4

What advantage do piezoelectric actuators offer over solenoid actuators?

Accepted Answer

A)   Faster response and lower power requirements.
B)   Much better dependability.
C)   Faster response and higher injection pressures.
D)   Cheaper to manufacture.

Question 5

Technician A states whenever a electrohydraulic injector is changed-out the PCM needs to be programmed with the new injectors calibration code. Technician B states that if a electrohydraulic injector is moved from on cylinder to another, PCM re-programming is not required. Who is correct?

Accepted Answer

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

Question 6

What is the key feature of electrohydraulic nozzles?

Accepted Answer

A)   They have fixed opening and closing pressure values.
B)   They require very little power to operate.
C)   They open and close independently from PCM commands.
D)   They do not have fixed opening and closing pressure values.

Question 7

What is the nozzle closing pressure (NOP)  equivalent to on a typical hydraulic injector?

Accepted Answer

A)   10 to 20 percent lower than the NOP.
B)   10 to 20 percent higher than NOP.
C)   Equal to NOP.
D)   99.9 percent of the NOP. A

Question 8

Testing EHIs on a computerized test bench will produce what type of results?

Accepted Answer

A)   An estimate of remaining service life.
B)   A detailed evaluation of each sub-component in the EHI.
C)   A detailed report of EHI performance over a range of conditions.
D)   OK or Not OK.

Question 9

When replacing contemporary injectors, what needs to be programmed into the PCM?

Accepted Answer

A)   Injector calibration codes.
B)   The injector service bit need to be reset to 0.
C)   Which injectors were changed by cylinder number.
D)   Nozzle opening pressure values.

Question 10

What component uses either a solenoid or piezoelectric actuator to operate?

Accepted Answer

A)   Pencil injectors.
B)   Common rails.
C)   Unit injectors.
D)   Electrohydraulic Injectors.

Question 11

What type of fuel injectors are required an almost all post 2007 diesel engines?

Accepted Answer

A)   Electrohydraulic injectors.
B)   Hydraulic.
C)   Mechanical.
D)   Electronic unit injectors.

Question 12

What are the two types of actuator used in electrohydraulic injectors?

Accepted Answer

A)   Mechanical and solidstate.
B)   Solenoid and servo.
C)   Servo and piezoelectric.
D)   Solenoid and piezoelectric.

Question 13

What is a hydraulic injector test bench fixture commonly referred to as?

Accepted Answer

A)   Nozzle valve tester.
B)   Electronic service tool.
C)   Pop tester.
D)   Ultrasonic bath.

Question 14

What component defines the exact distance an injector nozzle tip protrudes into the cylinder?

Accepted Answer

A)   Nozzle seat.
B)   Cylinder head injector seat.
C)   Nozzle spacer.
D)   Injector springs.

Question 15

What do most manufacturers specify about their common rail (CR)  high pressure lines?

Accepted Answer

A)   They have a pre-determined service life.
B)   They can be reinstalled only once.
C)   They should never be removed other than in a OEM factory environment.
D)   They are single-use components. D

Question 16

What is the highest pressure a fuel injection system can produce referred to as?

Accepted Answer

A)   Maximum pressure.
B)   Fuel compressibility limit.
C)   Peak pressure.
D)   Burst pressure.

Question 17

Technician A states that older hydraulic injectors were calibrated to open and close at a specific hard-value pressure known as nozzle opening pressure (NOP) . Technician B states that current injectors have a variable NOP controlled by the PCM. Which technician is correct?

Accepted Answer

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

Question 18

What feature is eliminated or reduced in size on valve closes orifice (VCO)  nozzles?

Accepted Answer

A)   Pressure chamber.
B)   Sac.
C)   Lower pressure chamber.
D)   Valve control chamber.

Question 19

How does the PCM control the EHI?

Accepted Answer

A)   By sending data directly to the EHI via the databus.
B)   Via the injector control unit.
C)   Using a digital to analog converter chip.
D)   Using a pulse-width modulated (PWM)  electrical charge. D

Question 20

What is the function of the nozzle sac used in hydraulic injectors?

Accepted Answer

A)   Hydraulically balances the fuel charge before injection.
B)   Retain a constant supply of fuel close to the injection nozzle.
C)   Slightly heat the fuel charge before injection.
D)   Hydraulically absorb pressure wave reflections during injector events.

Exam 8: Injector Nozzles

How is the piezo stack in a EHI linked to the control valve?

Correct AnswerverifiedShow Answer

What determines the injectors nozzle opening pressure (NOP) in a hydraulic injector?

Correct AnswerverifiedShow Answer

What is the practice of dividing an injection pulse into several injection pulses during a single intake cycle referred to as?

Correct AnswerverifiedShow Answer

What advantage do piezoelectric actuators offer over solenoid actuators?

Correct AnswerverifiedShow Answer

Technician A states whenever a electrohydraulic injector is changed-out the PCM needs to be programmed with the new injectors calibration code. Technician B states that if a electrohydraulic injector is moved from on cylinder to another, PCM re-programming is not required. Who is correct?

Correct AnswerverifiedShow Answer

What is the key feature of electrohydraulic nozzles?

Correct AnswerverifiedShow Answer

What is the nozzle closing pressure (NOP) equivalent to on a typical hydraulic injector?

Correct AnswerverifiedA

Testing EHIs on a computerized test bench will produce what type of results?

Correct AnswerverifiedShow Answer

When replacing contemporary injectors, what needs to be programmed into the PCM?

Correct AnswerverifiedShow Answer

What component uses either a solenoid or piezoelectric actuator to operate?

Correct AnswerverifiedShow Answer

What type of fuel injectors are required an almost all post 2007 diesel engines?

Correct AnswerverifiedShow Answer

What are the two types of actuator used in electrohydraulic injectors?

Correct AnswerverifiedShow Answer

What is a hydraulic injector test bench fixture commonly referred to as?

Correct AnswerverifiedShow Answer

What component defines the exact distance an injector nozzle tip protrudes into the cylinder?

Correct AnswerverifiedShow Answer

What do most manufacturers specify about their common rail (CR) high pressure lines?

Correct AnswerverifiedD

What is the highest pressure a fuel injection system can produce referred to as?

Correct AnswerverifiedShow Answer

Technician A states that older hydraulic injectors were calibrated to open and close at a specific hard-value pressure known as nozzle opening pressure (NOP) . Technician B states that current injectors have a variable NOP controlled by the PCM. Which technician is correct?

Correct AnswerverifiedShow Answer

What feature is eliminated or reduced in size on valve closes orifice (VCO) nozzles?

Correct AnswerverifiedShow Answer

How does the PCM control the EHI?

Correct AnswerverifiedD

What is the function of the nozzle sac used in hydraulic injectors?

Correct AnswerverifiedShow Answer

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A

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D

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D

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