Deck 21: Injector Nozzles

Question 1

What are the functions of a typical hydraulic injector nozzle?

A) define nozzle opening pressure (NOP)
B) atomize the fuel charge
C) target fuel to the correct area of the engine cylinder
D) all of the above

Answer 1

all of the above

Question 2

What is another way of saying popping pressure?

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

Answer 2

NOP

Question 3

What type of injector nozzles are used with today's direct injected engines?

A) poppet and pintle
B) pencil
C) multi-orifice and electrohydraulic
D) mechanical and pneumatic

Answer 3

multi-orifice and electrohydraulic

Question 4

Technician A says that multi-orifice hydraulic injectors have hard value NOPs. Technician B says that NOPs in electrohydraulic injectors (EHIs) have variable NOPs that are controlled by the ECM. Who is correct?

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

Question 5

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?

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

Question 6

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

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 7

Which of the following correctly describes atomization?

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 8

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

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

Question 9

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

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

Question 10

Identify the nozzle capable of soft opening pressures?

A) electrohydraulic (EHI)
B) multi-orifii in EUIs
C) pintle
D) pencil

Question 11

If a 4-stroke cycle diesel engine is run at 2000 rpm, how much real time is required for a single revolution of the engine?

A) 5 milliseconds
B) 15 milliseconds
C) 30 milliseconds
D) 60 milliseconds

Question 12

If injector valve-to-nozzle body clearance in a multi-orifii injector is greater than specification, which of the following values would increase?

A) NOP
B) peak pressure
C) back leakage
D) residual line pressure

Question 13

What is a typical NOP value of the multi-orifice nozzle used in an EUI (electronic unit injector)?

A) 800 psi
B) 2000 psi
C) 3000 psi
D) 5000 psi

Question 14

When multi-orifice nozzles are used in hydromechanical diesel engines, what would be a typical NOP value?

A) 5000 psi
B) 3000 psi
C) 2000 psi
D) 800 psi

Question 15

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

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

Question 16

The highest pressure that a diesel injection circuit is subject to is known as:

A) maximum system pressure
B) peak pressure
C) collapse pressure
D) NOP

Question 17

As pressure increases in the injection circuit, what happens to the emitted droplet sizing?

A) increases in size
B) decreases in size
C) becomes less aerated
D) becomes more aerated

Question 18

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

Question 19

Which of the following components in a multi-orifice hydraulic injector is constantly exposed to line pressure?

A) nozzle valve seat
B) nozzle valve stem
C) nozzle valve spring
D) nozzle pressure chamber

Question 20

What is the geometric relationship between the sectional area of the nozzle seat, and that of the nozzle pressure chamber known as?

A) nozzle differential ratio
B) seat to shank ratio
C) NOP to line pressure ratio
D) peak pressure to NOP ratio

Question 21

When a multi-orifice injector nozzle is closed, what seals the nozzle assembly from the engine cylinder?

A) nozzle sac
B) nozzle shank
C) nozzle line nut
D) nozzle valve seat

Question 22

What pressure is dead volume fuel held at in pump-line-nozzle (PLN) diesel fuel systems?

A) charging pressure
B) delivery valve opening pressure
C) nozzle opening pressure
D) residual line pressure

Question 23

Which type of multi-orifice injector nozzle sometimes uses an accumulator in place of a leakoff circuit?

A) pencil injectors
B) valve closes orifice (VCO)
C) high spring injectors
D) low spring injectors

Question 24

A hydraulic injector nozzle that uses a sacless design is known as:

A) pencil injector
B) low spring injector
C) valve closes orifice (VCO) injector
D) high spring injector

Question 25

What is required to test the NOP of a hydraulic injector?

A) OEM software
B) bench test fixture
C) ultrasonic bath
D) pressure pulse, line transducer

Question 26

Which of the following tools can be used to pull a flanged hydraulic injector nozzle from a cylinder head?

A) pry bar
B) injector heel bar
C) injector sleeve broach
D) screwdriver

Question 27

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

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 28

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

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

Question 29

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

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

Question 30

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

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

Question 31

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

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

Question 32

When attempting to remove a seized injector spacer washer, which of the following tools would be recommended?

A) taper reamer
B) heel end of an injector heel bar
C) tapered end of an injector heel bar
D) hammer and punch

Question 33

Which of the following is another way of saying injector bench test fixture?

A) pop tester
B) ultrasonic bath
C) nozzle orifice reamer
D) lapping block

Question 34

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

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

Question 35

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

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 36

While bench testing a multi-orifice injector nozzle, it rapidly pulses (chatter) as NOP is achieved. Technician A says that the nozzle seat is defective and should be replaced. Technician B says that nozzle chatter usually occurs only during bench testing. Who is right?

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

Question 37

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

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

Question 38

When adjusting a low spring injector nozzle NOP, what should be done to increase opening pressure?

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

Question 39

Technician A says that after replacing an injector spring on a hydraulic multi-orifice injector, it is good practice to set NOP 75 psi above specification. Technician B says that any time a hydraulic nozzle assembly is reassembled after bench testing, it is good practice to set NOP 150 psi above specification. Who is right?

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

Question 40

When nozzle back leakage is higher than specification, this is usually an indication of:

A) wear
B) nozzle valve cavitation
C) nozzle seat erosion
D) injector spring fatigue

Question 41

What is the advantage of piezo actuators over solenoid actuators?

A) lower cost
B) lighter weight
C) faster response
D) higher peak pressure potential

Question 42

When considering EHI operation in a standard CR system while the engine is running but the actuator is not energized which of the following is true?

A) rail pressure is at nozzle needle seat
B) rail pressure is present in the upper pressure field
C) the upper and lower pressure fields are at the same pressure
D) all of the above

Question 43

What force(s) hold an EHI nozzle needle seated in a standard CR system when the engine is stationary and there is no measurable rail pressure?

A) hydraulic pressure only
B) spring pressure only
C) electrical pressure only
D) combined spring and electrical force

Question 44

In a running engine with a CR diesel system, what force(s) hold the nozzle needle seated when the actuator is not energized?

A) hydraulic force only
B) spring force only
C) electrical force only
D) combined spring and hydraulic force

Question 45

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

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

Question 46

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

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

Question 47

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?

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

Question 48

What determines the soft opening and closing values of EHIs in any given moment of engine operation?

A) rail pressure
B) electrical pressure at injector driver
C) ECM
D) engine rpm

Question 49

Technician A says that high pressure fuel can exit an injector nozzle at faster than the speed of sound. Technician B says that the most OEMs recommend electrohydraulic injectors (EHIs) to be field serviced using standard shop tools. Who is correct?

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

Question 50

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?

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

Question 51

?Technician A says that EHIs are ECM switched to open and close. Technician B says that EHIs are opened when pressure in the CR rises to the nozzle opening pressure. Who is correct?

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