Deck 30: Common Rail Systems

Question 1

Technician A says that the first generation of diesel common rail (CR) systems was introduced on small bore diesel engines. Technician B says that CR fuel systems are unable to produce high enough peak pressures to fuel current large bore diesel engines. Who is correct?

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

Answer 1

Technician A only

Question 2

How many high pressure pumps are required to fuel a typical inline 6-cylinder, CR-fueled engine?

A) One
B) Two
C) Three
D) Six

Answer 2

One

Question 3

Technician A says that in a diesel CR fuel system, the rail supplies all of the injectors required to fuel the engine. Technician B says that the rail pressures in a diesel CR fuel system are widely variable. Who is correct?

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

Answer 3

Both A and B

Question 4

What type of fuel system is used on EPA MY 2010 and later Cummins ISX engines?

A) CAPS
B) HPI-TP
C) EUI
D) XPI

Question 5

What component is used to control the actual rail pressure of a CR diesel fuel system?

A) rail pressure sensor
B) rail pressure control valve
C) EHI solenoid
D) accumulator

Question 6

Technician A says that desired rail pressure in a CR fuel system is signaled by the rail pressure sensor. Technician B says that actual rail pressure in a CR fuel system is calculated 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 7

What type of injectors are used in a typical diesel CR system?

A) Pintle injectors
B) Poppet injectors
C) Multi-orifice injectors
D) Electrohydraulic injectors (EHIs)

Question 8

Which of the following components serves as the accumulator in a typical diesel CR fuel system?

A) Hydraulic head
B) Rail
C) Pump chamber
D) Amplifier chamber

Question 9

Technician A says that the actuation voltage used to drive CR electrohydraulic injectors (EHIs) is typically around 100 volts when they use solenoid actuators. Technician B says that EHI piezo actuator resistance reading tend to be higher solenoid-actuated EHIs, for EHIs that use piezo actuators is usually much higher than 100 volts. Who is correct?

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

Question 10

What is used to switch an electrohydraulic injector (EHI) used in a typical CR fuel system?

A) Pulse width modulated signal
B) Analog voltage charge
C) Fuel volume in accumulator
D) Hydraulic distributor head

Question 11

Which of the following best describes the type of pump used with typical Bosch CR fuel systems?

A) Rotary distributor
B) In-line plunger
C) Radial piston
D) Opposed plunger

Question 12

How many plungers are used in the high pressure section of a Bosch radial piston pump?

A) One
B) Two
C) Three
D) Six

Question 13

Technician A says that an advantage of EHIs over standard hydraulic injectors, is the absence of injection lag. Technician B says that EHIs are capable of multipulse injections within a single cycle. Who is correct?

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

Question 14

What would happen if an EHI used on a Bosch CR fuel system stuck in an open position?

A) Fuel rail pressure would collapse
B) Immediate engine shutdown
C) Cylinder would overfuel
D) Flow limiter would limit fueling

Question 15

Technician A says that EHI pressure at the beginning of an injection pulse should be closely equivalent to rail pressure. Technician B says that EHI pressure at the end of an injection pulse will have dropped off significantly. Who is correct?

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

Question 16

Technician A says that the ECMs used on commercial truck applications of diesel CR are networked on the CAN-C bus. Technician B says that the diesel engine ECMs used on automobile and light truck applications of diesel CR are networked exclusively by the J1939 bus.Who is correct?

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

Question 17

What is used to lubricate the high pressure radial piston pumps used on most Bosch CR fuel systems?

A) Fuel
B) Isolated oil supply
C) Engine lubrication circuit
D) Lubriplate

Question 18

What type of high pressure pump do Caterpillar use in their CR fuel systems?

A) Port-helix
B) Inline piston
C) Radial piston
D) External gear

Question 19

Technician A says that fuel delivery timing in diesel CR fuel systems is limited by cam profile. Technician B says that a major advantage of diesel CR systems is their ability to manage fuel injection pressures without regard to engine rpm. Who is correct?

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

Question 20

Technician A says that all current diesel CR fuel systems use a transfer pump. Technician B says that Caterpillar flange mount their transfer pump to the CR high pressure pump. Who is correct?

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

Question 21

Technician A says that most transfer pumps used on diesel CR systems are of the external gear type. Technician B says that most transfer pumps used on diesel CR systems use a non-positive pumping principle. Who is correct?

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

Question 22

How many pump cylinders are used in a Caterpillar CR system high pressure pump?

A) one for each engine cylinder
B) three
C) two
D) one

Question 23

Technician A says that most Bosch CR high pressure pumps are lubricated with diesel fuel. Technician B says that Caterpillar CR high pressure pumps are lubricated with engine oil. Who is correct?

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

Question 24

If actual rail pressure falls below desired rail pressure in a diesel CR system, which of the following should occur?

A) rail pressure control valve options more fuel to the return circuit
B) rail pressure control valve directs more flow to the rail
C) rail flow limiter reduces flow to the EHIs
D) rail flow limiter temporarily cuts flow to the EHIs

Question 25

If the rail pressure limiter valve trips open in a typical CR fuel system, which of the following should be true?

A) rail pressure has exceeded the highest specified system pressure
B) an EHI injection pulse is taking place
C) actual rail pressure has fallen below desired rail pressure
D) an EHI has stuck in the open position

Question 26

What is the function of the quill tube used in many diesel CR systems?

A) connects the CR high pressure pump to the rail
B) connects the transfer pump to the secondary filter
C) vents the fuel tank to atmosphere
D) connects the rail high pressure pipes to the EHIs through the cylinder head

Question 27

When a CR high pressure line is removed for any reason, which of the following steps is required practice by many engine OEMs?

A) remove and replace the line nuts
B) torque the line nuts to spec
C) dress the sealing nipples on a grinder
D) replace the high pressure line

Question 28

Which of the following is another way of saying base timing when referring to multipulse capable, CR fuel systems?

A) start of first injection pulse
B) end of final injection pulse
C) start of dosing pulse
D) end of dosing pulse

Question 29

When a typical CR-EHI is energized by the injector driver, which of the following occurs first?

A) pressure in the valve control chamber rises
B) pressure in the valve control chamber collapses
C) an injection pulse begins
D) an injection pulse

Question 30

Technician A says that CR EHIs with piezo actuators respond faster to energization by the injector drivers than those with solenoid actuators. Technician B says that current CR EHIs using piezo actuators tend to be slimmer and more compact than those with solenoid actuators. Who is correct?

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

Question 31

What term is used by Caterpillar on their CR EHIs to code their injection quantity calibration data for programming to the ECM?

A) quick response (QR) code
B) E-Trim
C) Cal code
D) Set point

Question 32

Technician A says that an EHI with a piezo actuator is capable of breaking up a single injection cycle into up to 7 separate pulses. Technician B says that during a CR EHI multipulse injection cycle, the pressure rises through each successive pulse. Who is correct?

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

Question 33

What explains why EHIs with Piezo actuators respond faster to energization signals from the injector drivers?

A) mechanical movement at the actuator does not depend on building a magnetic field
B) piezoelectric signals travel faster
C) piezo actuators are lighter in weight than solenoid actuators
D) piezo actuators consume much more electricity than solenoid actuators

Question 34

Technician A says that adaptive trim (A-Trim) evaluates and corrects EHI fuel flow at set intervals to ensure balanced cylinder fueling. Technician B says the A-Trim feature makes initial fuel flow programming (E-Trim/ QR-codes/ Cal-codes) unnecessary. Who is correct?

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

Question 35

What is used to time a Caterpillar CR fuel system high pressure pump to the engine?

A) spill timing
B) electronic timing
C) timing pin
D) high pressure phasing

Question 36

What is the function of the admission valve used in some diesel CR fuel systems?

A) prevents fuel siphon from the rail on shutdown
B) holds rail pressure fuel away from nozzle seat until energized
C) monitors fuel quantity entering the CR pump
D) restricts flow area of the rail inlet

Question 37

What force is used to hold the nozzle valve seated and closed on a typical CR-EHI when the engine is running?

A) Combined spring and hydraulic force
B) Combined spring and electrical force
C) Spring force only
D) Electrical force only

Question 38

Which of the following best explains why some OEMs state that the high pressure pipes used on CR systems should not be re-used?

A) the line nut hex is easily rounded out
B) the engine warranty will voided
C) it is more profitable to the OEM to sell as many parts as possible
D) the seats deform to seal when initially torqued

Question 39

Which of the following is the ECM output used to manage rail pressure at any given moment of operation in a diesel CR fuel system?

A) rail pressure sensor
B) rail flow limiter valve
C) EHI actuators
D) rail pressure control valve

Question 40

Technician A says that an advantage of CR-EHIs is that they are less susceptible to problems caused by contaminated fuel than other types of fuel injector. Technician B says that when a CR-EHI fails due to contaminated fuel, the problem can be usually rectified by disassembly, cleaning, and reassembly. Who is correct?

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

Question 41

?Which of the following engine OEMs uses a Delphi CR fuel system?

A) ?Caterpillar
B) ?Paccar
C) ?Navistar
D) ?Hino

Question 42

?Technician A says that MY 2013 and later Paccar MX engines use a pair of EUPs to supply the common rail with high pressure fuel. Technician B says that Paccar PX engines use a Bosch CR fuel system. Who is correct?

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