Deck 19: Fuel Subsystems

Question 1

Which of the following fuel subsystem components would typically be located closest to the fuel tank?

A) primary filter
B) transfer pump
C) injection pump
D) secondary filter

Answer 1

primary filter

Question 2

Which of the following components would NOT be under suction when the engine is running?

A) primary filter
B) pickup tube
C) fuel tank
D) secondary filter

Answer 2

secondary filter

Question 3

In a typical diesel fuel subsystem, where would the fuel subsystem charging pressure regulating valve be located?

A) in the pick-up tube
B) in the primary filter pad
C) after the transfer pump
D) before the transfer pump

Answer 3

after the transfer pump

Question 4

Which of the following fuel subsystem components would be subjected to charging pressure?

A) fuel transfer pump inlet
B) primary filter
C) pick-up tube
D) secondary filter

Question 5

Which diesel engine manufacturer is noted for the fact that some of their fuel subsystems are entirely under suction?

A) Caterpillar
B) Cummins
C) Detroit Diesel
D) Mack Trucks

Question 6

Which of the following is NOT generally considered to be a desirable feature specified to a truck fuel tank?

A) aluminum construction
B) cylindrical shape
C) temperature insulated
D) located in airflow

Question 7

Which of the following is the critical electrical component of a diesel fuel tank sending unit?

A) float
B) variable resistor
C) thermistor
D) low fuel warning light

Question 8

What should be used to verify the operation of a fuel tank sending unit when it is electrically disconnected?

A) DMM ohmmeter
B) DMM ammeter
C) dash display diagnostics
D) master gauge

Question 9

When a single pick-up tube is used on a pair of cylindrical fuel tanks mounted either side of a truck frame, which of the following is required?

A) auxiliary pump
B) two return lines
C) two transfer pumps
D) crossover pipe

Question 10

When water is present in the fuel tanks of a dual tank, single pickup fuel subsystem, where is it likely to settle?

A) on top of the tank
B) emulsify in the fuel
C) in the pick-up tube
D) crossover pipe

Question 11

Technician A says that when a diesel fuel tank is vented to atmosphere, more than half the dirt trapped by the fuel filters enters the tank through the breather. Technician B says that a fuel tank breather filter can extend the life of fuel filters. Who is correct?

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

Question 12

In conditions of extreme heat in most diesel fuel systems, what happens to diesel fuel vapors boiled off from the fuel in the fuel tanks?

A) vented to atmosphere
B) exit pick-up tube causing vapor lock
C) charged to a carbon canister
D) create high tank pressures

Question 13

What is the correct method used to determine if water is present in a diesel fuel tank?

A) drain tank and visually inspect
B) add a dye penetrant fluid
C) use water detection paste on a probe
D) drain sump and send for lab analysis

Question 14

You are checking for water in fuel using water detection paste on a probe and just the tip of the probe changes color. What should you do?

A) nothing, this is normal
B) add a quart of methyl hydrate
C) drain the tank and refuel
D) contact the fuel supplier and ask for a refund

Question 15

When a leak is identified in an aluminum fuel tank, what do most manufacturers recommend?

A) fill tank with water and weld
B) steam tank, fill with nitrogen and weld
C) repair with silicone
D) replace tank

Question 16

When you are asked to repair weld an aluminum diesel fuel tank, which of the following is recommended?

A) fill with fuel before welding
B) fill with water before welding
C) steam and fill with nitrogen
D) steam and fill with oxygen

Question 17

In a typical fuel subsystem, which of the following is capable of entrapping the smallest particles suspended in the fuel?

A) primary filter
B) fuel/ water separator
C) pre-strainer
D) secondary filter

Question 18

When testing for fuel subsystem inlet restriction which of the following is recommended?

A) positive pressure gauge reading in inches of water
B) positive pressure gauge reading in inches of mercury
C) negative pressure gauge reading in inches of mercury
D) plumb an air filter restriction gauge into the primary filter pad

Question 19

When priming a primary fuel filter during a routine service, which of the following is best practice?

A) pressurize the fuel tanks with shop air
B) crank the engine for 30 seconds
C) pour fuel only into filter inlet ports
D) pour fuel only into filter outlet port

Question 20

When priming a new secondary filter, which method do most OEMs prefer you use?

A) pressurize the fuel tanks
B) a hand, electric, or integral primer pump
C) pour fuel only into filter inlet ports
D) pour fuel only into filter outlet port

Question 21

What would double gasketing of a primary fuel filter most likely cause?

A) fuel leakage
B) no-start condition
C) sucking air into fuel
D) vapor lock

Question 22

What is a fuel water separator unable to remove from the fuel routed through it?

A) free state water
B) emulsified water
C) semi-absorbed water
D) coalesced water

Question 23

When comparing the properties of diesel fuel with water, which of the following is NOT true of diesel fuel?

A) more compressible
B) higher lubricity
C) lower freeze point
D) promotes corrosion

Question 24

What two principles are used by most fuel water separators to remove water from fuel?

A) centrifugal force and gravity
B) positive filtration and straining
C) emulsification and absorption
D) absorption and condensation

Question 25

What pumping principle is used on transfer pumps on a majority of diesel engines today?

A) reciprocating plunger
B) centrifugal
C) gear
D) swash plate

Question 26

What pumping principle is used by hand-actuated priming pumps on most current diesel fuel subsystems?

A) reciprocating plunger
B) centrifugal
C) gear
D) vane

Question 27

In order to prime a typical fuel sub-system with a hand-primer pump that has to be installed into the circuit, where should it ideally be located?

A) close to the pick-up tube
B) upstream from the primary filter
C) upstream from the transfer pump
D) downstream from the secondary filter

Question 28

What can result from a water-in-fuel condition when the secondary filter is capable of entrapping particulate as small as one micron?

A) filter burst
B) plugged filter and shutdown
C) filtering media failure
D) water absorption into fuel

Question 29

What should be used to diagnose an air-in-fuel condition in a diesel fuel sub-system?

A) on-board diagnostic software
B) mercury manometer
C) ether
D) diagnostic sight glass

Question 30

When a fuel heater is used in a diesel fuel sub-system, what is the maximum temperature the fuel should be heated to?

A) 75 degrees Fahrenheit
B) 90 degrees Fahrenheit
C) 110 degrees Fahrenheit
D) 125 degrees Fahrenheit

Question 31

What device is used to sense the presence of water within a fuel filter and alert the driver?

A) Thermistor
B) WIF sensor
C) Potentiometer
D) CTS sensor

Question 32

What is the currently recommended method of filling a new secondary fuel filter following a filter service?

A) charge air tanks with shop air
B) install an auxiliary electric pump into the fuel sub-system
C) hand or electric pump prime after installation
D) fill with fuel prior to installation onto the filter mounting pad

Question 33

A small quantity of water is drained from a water separator equipped with a WIF sensor that has produced no service alert. Immediately after, a WIF alert is signaled. What should you do first?

A) Replace the water separator
B) Replace the WIF sensor
C) Check the fuel tanks for water
D) Clean the WIF probes

Question 34

When troubleshooting the root cause of a diesel injector in which the tip has been blown off, which of the following should be checked first?

A) lubricity of diesel fuel
B) API gravity of fuel
C) methyl hydrate in fuel condition
D) water-in-fuel condition

Question 35

An engine with a reported lack of power (LOP) condition evidently caused by fuel starvation is being diagnosed. The specified maximum inlet restriction on the primary side of the fuel transfer pump is 7-inches HG and the circuit tests at exactly this value. Technician A says that the LOP condition is almost certainly caused by a plugged primary filter and the first step should be to change it. Technician B says that the primary side of the fuel subsystem is not responsible because it still tests within specification. Who is correct?

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

Question 36

Technician A says that secondary fuel filters can entrap particles smaller than the eye can see. Technician B says that primary filters cannot entrap particles smaller than a section of a human hair. Who is correct?

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

Question 37

You are verifying the performance of a 240-ohm fuel tank sending unit that you have disconnected. Which of the following resistance readings is OK when the sender arm is moved to the full fuel position?

A) 230 ohms
B) 90 ohms
C) 30 ohms
D) 0 ohms

Question 38

When fuel exits a gear pump discharge port while an engine is run, what force moves more fuel into the gear pump inlet in a typical diesel fuel subsystem?

A) gravity
B) atmospheric pressure
C) charging pressure
D) injection pressure

Question 39

Technician A says that a diesel fuel tank plays a role as a heat exchanger in many modern diesel fuel systems. Technician B says that rectangular shaped fuel tanks can provide the same strength using thinner wall thickness than that required for cylindrical tanks. Who is correct?

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

Question 40

What do Caterpillar define as the maximum amount of water content in a diesel fuel if it meets their standards for clean fuel?

A) 0.0015%
B) 0.01%
C) 0.10%
D) 1%

Question 41

Which of the following sensors would least likely be used in a current fuel subsystem?

A) charging pressure sensor
B) fuel pressure sensor
C) water-in-fuel sensor
D) inductive pulse sensor

Question 42

In a fleet operation, when should truck drivers be instructed to refill the fuel tanks?

A) immediately after returning from a trip
B) before beginning their outbound trip
C) when the ambient temperature is lowest
D) never, it should be done by a yard jockey

Question 43

Technician A says that diesel fuel is potentially explosive and should be handled with great care during refilling operations especially in the heat of summer. Technician B says that refueling diesel fuel tanks while smoking a cigarette is not advisable. Who is correct?

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

Question 44

?Technician A says that a diesel fuel subsystem secondary filter can plug on water causing an engine shutdown. Technician B says that when secondary fuel filter causes an engine shutdown due to fuel starvation, pouring two cans of methyl hydrate into the fuel tank should cure the problem. Who is correct?

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

Question 45

?Technician A says that some diesel post-2007 diesel engines fitted with DPFs use a dosing injector. Technician B says that diesel fuel subsystem charging pressure values can be much higher in engines that use dosing injectors. Who is correct?

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

Question 46

Technician A says that it is common for Caterpillar HEUI fuel systems to use a centrifugal type fuel transfer pump. Technician B says that a double-acting fuel subsystem transfer pump moves fuel on the push and pull strokes. Who is correct??

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

Question 47

Where would you most likely find a WIF sensor? ?

A) ?Fuel tank
B) ?Primary filter assembly
C) ?Secondary filter assembly
D) ?Common rail

Question 48

When is the preferred time to refuel diesel fuel tanks??

A) ?When completely emptied
B) ?When 50% drained
C) ?Early in the morning
D) ?Before parking after returning from a trip

Question 49

Technician A says that the best way to prime a diesel fuel system is to charge shop air pressure to the fuel tank and crank the engine unit it fires. Technician B says that when a fuel subsystem is fitted with an ECM-managed priming pump, this should always be used to prime the engine after a service. Who is correct? ?

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