Deck 9: Functions of High Pressure Fuel Systems

Question 1

Which engine exhaust emission can be significantly reduced by using pilot injection (split-shot injection)?

A)Particulate matter (PM).
B)NOx.
C)Carbon monoxide (CO).
D)Carbon dioxide (CO₂).

Answer 1

B

Question 2

Consider an engine that is satisfactorily operating on all cylinders. If one cylinder is cut out for testing, what will happen to the pulse width (electrical signal time) of the remaining injectors?

A)The pulse width will shorten to maintain engine speed.
B)The pulse width will lengthen to maintain engine speed.
C)The pulse width will shorten to compensate for the missing injector.
D)The pulse width will lengthen to compensate for over-fueling the injectors.

Answer 2

B

Question 3

A slow buildup of the fuel-injection rate (ramp-shaped injection rate) for the main injection reduces which of the following emissions?

A)Oxides of nitrogen (NOx).
B)Particulate matter (PM).
C)Carbon monoxide (CO).
D)Hydrocarbons (HCs).

Answer 3

A

Question 4

Technician A says a long injector response time from a magnetic solenoid is due mostly to the speed of the electric current through long wire windings. Technician B says a long injector response time is caused primarily by heavy, high-inertia control valves. Who is correct?

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

Question 5

While discussing the steps to perform when changing an injector in a late-model engine, Technician A says that uploading a fuel injector calibration code helps the engine to run more smoothly. Technician B says that replacing the old code with the one on the new injector enables the ECM to compensate for small variations to injection quantity unique to each injector. Who is correct?

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

Question 6

While checking contributions from each cylinder for a late-model electronically controlled engine, Technician A says that the purpose of adaptive cylinder balance is to reduce combustion noise so that diesels run more quietly. Technician B says adaptive balance reduces emissions and helps an engine run more smoothly. Who is correct?

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

Question 7

Technician A says that when a diesel engine has an increased load and its speed remains constant, injection timing must advance. Technician B says that under those conditions, injection timing should retard. Who is correct?

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

Question 8

After assembling an engine and discovering one of the vibration-insulating high-pressure fuel line clamps was missing, two technicians discussed potential consequences of the clamp remaining missing from the injector line. Technician A says that the line will crack due to vibration caused by pressure pulses. Technician B says that a single missing clamp on thick-walled steel lines will have no effect on the line. Who is correct?

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

Question 9

Technician A says that cutting out one cylinder at idle to check for a misfire condition will reduce idle speed by close to 100 rpm in a six-cylinder engine idling at 600 rpm if the cylinder is operating properly. Technician B says it is not possible to detect a misfiring cylinder at idle by noting a change in idle speed during cylinder cutout testing for any cylinder. Who is correct?

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

Question 10

Which of the following statements best describes ignition delay in a diesel engine?

A)The time required to raise fuel pressure high enough to overcome compression pressure in a cylinder.
B)The time lag from initial injection to actual ignition.
C)The time required to heat up a glow plug.
D)The time required for vaporized fuel to atomize.

Question 11

In which of the following ways does the rate at which combustion occurs change when additional fuel is added to a cylinder?

A)Combustion time is shortened.
B)Combustion time is lengthened.
C)Combustion time remains the same.
D)Combustion time is advanced.

Question 12

What injection strategy is best used to start, but not run, a cold engine?

A)Retarding injection timing.
B)Advancing injection timing.
C)Using a post-combustion injection.
D)Eliminating the pilot injection.

Question 13

Technician A says a slow buildup of the injection rate, which provides a ramp-shaped injection discharge rate shape for the main injection event and reduces CO emissions. Technician B says the ramp-shaped injection rate shape reduces NOx emissions. Who is correct?

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

Question 14

While discussing potential ways to increase power output from an engine, Technician A says that advancing injection timing a few degrees will increase power output. Technician B says that advancing injection timing a few degrees will reduce fuel consumption. Who is correct?

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

Question 15

Which of the following is the most significant benefit of pilot injection?

A)Better fuel economy.
B)Lower combustion chamber noise.
C)Longer ignition delay.
D)Precise injection timing.

Question 16

How does pilot injection, also known as split-shot injection, reduce exhaust emissions?

A)Main injection timing can be advanced.
B)Combustion time enables a more complete burn of poorly atomized fuel.
C)Cylinder temperatures increase near top dead center (TDC).
D)Main injection timing can be retarded.

Question 17

Consider a diesel engine that has an increased load applied to it while its speed remains constant. Which of the following changes to injection timing would be expected?

A)An advance in injection timing.
B)A delay in injection timing.
C)No change to injection timing.
D)Retarded injection timing.

Question 18

Technician A says that multiple injection events from an injector to reduce emissions results in less torque produced from an engine. Technician B says that multiple injection events during a combustion cycle are used to reduce heat loads in a cylinder. Who is correct?

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

Question 19

The term "retarded injection timing" refers to injection timing occurring _________.

A)later than normal
B)earlier than normal
C)at top dead center (TDC)
D)at bottom dead center (BDC)

Question 20

While discussing possible causes of black smoke from the exhaust of an older heavy-duty diesel engine, Technician A says that black smoke from an engine under acceleration indicates the engine is producing plenty of power. Technician B says that smoke could indicate that the injector nozzle spray holes are worn out. Who is correct?

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

Question 21

Fuel is injected only near the end of the compression stroke, so these events must be performed quickly to allow adequate time for:

A)combustion"
B)the piston to move"
C)the fuel pressure to build
D)compression"

Question 22

What is the process called where the liquid fuel is broken up into a fine mist?

A)Carbonization"
B)Vaporation"
C)Atomization
D)Mixing"

Question 23

Which of the following is NOT a task performed by high-pressure injection systems?

A)Time the injection of fuel"
B)Control the rate of fuel delivery"
C)Atomize the fuel
D)Vaporize the fuel"

Question 24

Technician A says that atomization can be reduced with high injection pressures. Technician B says that high pressure is necessary to break up the liquid fuel into a fine mist. Who is right?

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

Question 25

Higher pressurization produces increasingly smaller droplets of fuel that readily absorb heat and burn while improving atomization that results in efficient combustion, as well as:

A)improved starting"
B)better fuel economy"
C)lower engine pressures
D)high blowby gases"

Question 26

Since 2007, throttle plates are used to help in the operation of:

A)mass air flow"
B)EGR"
C)SCR
D)the turbocharger"

Question 27

What is done when the road grade becomes steeper or additional freight and passengers are added to the vehicle?

A)Increase fueling"
B)Advance timing"
C)Retard timing
D)Reduce EGR"

Question 28

Technician A says that the operator is the only system that determines engine power output. Technician B says that diesel governors have several inputs, but only the throttle is controlled by the operator. Who is right?

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

Question 29

What device regulates the quantity of fuel injected into the cylinders?

A)Throttle valve"
B)Metering valve"
C)Governor
D)Injection pump plungers"

Question 30

Speed and torque output are controlled by:

A)controlling valve timing"
B)metering fuel"
C)opening the throttle
D)closing the throttle"

Question 31

While discussing the steps to perform when changing an injector in a late-model engine, Technician A says that uploading a fuel injector calibration code helps the engine to run more smoothly. Technician B says that replacing the old code with the one on the new injector enables the ECM to compensate for small variations to injection quantity unique to each injector. Who is correct?

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

Question 32

Technician A says that when a diesel engine has an increased load and its speed remains constant, injection timing must advance. Technician B says that under those conditions, injection timing should retard. Who is correct?

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

Question 33

Technician A says that cutting out one cylinder at idle to check for a misfire condition will reduce idle speed by close to 100 rpm in a six-cylinder engine idling at 600 rpm if the cylinder is operating properly. Technician B says it is not possible to detect a misfiring cylinder at idle by noting a change in idle speed during cylinder cutout testing for any cylinder. Who is correct?

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

Question 34

A speed density algorithm is an example of a mathematical procedure used to calculate:

A)fuel mass entering the cylinders"
B)exhaust out of the tailpipe"
C)air mass entering the cylinders
D)engine speed"

Question 35

What is observed when one or more cylinders are cut out and the engine maintains a set idle speed?

A)Compensation"
B)Metering"
C)Idle control
D)Valve timing"

Question 36

In which of the following ways does the rate at which combustion occurs change when additional fuel is added to a cylinder?

A)Combustion time is shortened."
B)Combustion time is lengthened."
C)Combustion time remains the same.
D)Combustion time is advanced."

Question 37

While discussing potential ways to increase power output from an engine, Technician A says that advancing injection timing a few degrees will increase power output. Technician B says that advancing injection timing a few degrees will reduce fuel consumption. Who is correct?

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

Question 38

Efficient fuel systems must have the capability to change the point when fuel is injected, based on a variety of engine operating conditions and:

A)control algorithms"
B)control systems"
C)control operations
D)control steps"

Question 39

What is the time period between the injection of fuel and its actual point of ignition called?

A)ignition delay"
B)ignition lag"
C)injection delay
D)injection lag"

Question 40

Under load, higher cylinder pressures and temperatures cause fuel to burn more completely, and only _____ should be observed coming from the engine exhaust system.

A)white smoke"
B)heat haze of hot air"
C)high hot air
D)grey smoke"

Question 41

Which of the following factors is NOT affected by injection rate control?

A)Fuel consumption"
B)Exhaust emissions"
C)Combustion noise
D)Valve timing"

Question 42

When referencing rate control of the injection system, the most meaningful definition is the quantity of fuel injected per:

A)revolution of the crankshaft"
B)revolution of the camshaft"
C)degree of cam angle rotation
D)degree of crank angle rotation"

Question 43

Injection rate is reported in which of these values as compared with the delivery volume of the injection event?

A)Milliseconds of crankshaft rotation"
B)Minutes of crankshaft rotation"
C)Degrees of crankshaft rotation
D)Seconds of crankshaft rotation"

Question 44

How many separate injection events can HPCR (high pressure common rail) systems currently provide during one combustion cycle?

A)8"
B)4"
C)5
D)7"

Question 45

The discharge shape on mechanical fuel injection systems is achieved by using:

A)a stepped-camshaft"
B)buttons in the injection pump"
C)a stepped-type nozzle valve
D)a hydraulic control valve"

Question 46

Two technicians are describing a mechanical fuel system. Technician A says that when the engine needs to rapidly accelerate, large injection quantities of high-pressure injection pressure are always available. Technician B says that small injection quantities distribute fuel too far and fast in the combustion chamber to provide the best combustion conditions. Who is right?

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

Question 47

Technician A says that fuel pressurized to thousands of pounds per square inch (psi) can easily penetrate the skin, causing bodily harm, blood poisoning, and even death. Technician B says that when checking for leaks from a high-pressure fuel system, use a small piece of cardboard or paper instead of the hand to detect the location of a leak. Who is right?

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

Question 48

Improved atomization requires higher:

A)distribution"
B)diffusion"
C)pressurization
D)mixing"

Question 49

Technician A says that fuel injection systems are electronically controlled with variable injection pressure capabilities and with maximum injection pressure reached independent of engine speed. Technician B says that improved atomization requires lower pressurization for improved emissions and performance. Who is right?

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

Question 50

Diesel engines compress dense air mass that requires ________ to penetrate the dense compressed air with fuel.

A)High air pressure"
B)High fuel pressure"
C)Low temperature
D)Low Sulphur content"

Question 51

Two technicians are describing fuel atomization. Technician A says that the ignition delay period is also lengthened, leading to lower levels of combustion noise. Technician B says that finer atomization means fuel ignites sooner, burns faster, and burns more completely. Who is right?

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

Question 52

What forms around the fuel droplet as it absorbs heat from the combustion chamber?

A)Liquid fuel"
B)Water vapor"
C)Haze
D)Fuel vapor"

Question 53

Using fine droplets also means that retarded injection timing can be used, to produce low:

A)NOx emissions"
B)HC (hydrocarbon) emissions"
C)CO (carbon monoxide) emissions
D)CO₂ (carbon dioxide) emissions"

Question 54

Under which of the following conditions is excessive particulate emissions NOT typically produced?

A)Large fuel droplet size"
B)Poor mixing of air and fuel"
C)Inadequate pre-ignition temperatures
D)Excessive combustion time"

Question 55

Which of the following does NOT result in large fuel droplet size?

A)Excessive fueling of combustion chamber"
B)Worn nozzles and spray holes"
C)Low injection pressures
D)Nozzle dribble"

Question 56

Newer diesel engines have about _____ holes as compared with only 4 or 5 in older engines.

A)6"
B)7"
C)20
D)13"

Question 57

Which of the following is NOT provided by fuel and air mixed by bowl turbulence?

A)Best power"
B)Low emissions"
C)Low EGR
D)Good fuel economy"

Question 58

The design of the delivery valve ensures fuel pressure drops far enough below nozzle opening pressure to prevent:

A)primary injections"
B)secondary injections"
C)high housing pressure
D)low housing pressure"

Question 59

What minimizes the backflow of fuel into an injection system in order to maintain line pressure between injections?

A)Metering valve"
B)Delivery valves"
C)PWM solenoid
D)Housing pressure control valve"

Question 60

Technician A says that vibration isolators clamped to common rail fuel lines are necessary to prevent lines from cracking. Technician B says that fuel-injection lines can have different diameters and length. Who is right?

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