DSL-202 Chap 27 Common Rail Fuel Systems

Maximum injection pressure is available at __________.

• a. Idle

• b. Full load

• c. Rated power

• d. All of these are correct.

Technician A says modern common rail (CR) refers to a classification of high-pressure fuel injection systems in which pressurization of fuel is accomplished independently of engine speed. Technician B says fuel injection pressure is matched to optimal values required for the most efficient combustion, lowest emissions, highest power output, and best fuel economy. Who is correct?

• a. Technician A

• b. Technician B

• c. Both Technician A and Technician B

• d. Neither Technician A nor Technician B

Technician A says the basic concept of common rail injection is simple: supply fuel at injection pressure to a fuel nozzle that electrically controls the injection event. Technician B says the common rail system's modular design lends flexibility for adaptation to any new or updated diesel engine design. Who is correct?

• a. Technician A

• b. Technician B

• c. Both Technician A and Technician B

• d. Neither Technician A nor Technician B

What do greater rate-shaping capabilities do?

• a. Lower emissions

• b. Lower fuel consumption

• c. Maintain engine performance

• d. All of these are correct

The name "common rail" may also be called __________.

• a. Fuel line and rail system

• b. High-pressure accumulator rail system

• c. Rail system

• d. Fuel gallery system

Beginning of injection occurs when the __________.

• a. Ball valve closes

• b. Ball valve lifts

• c. Electrical current collapses

• d. Servo valve closes

Technician A says the difference between the CRS1 and CRS2 injectors is in the nozzle. Technician B says the nozzle valve closing speed is determined by the flow through the inlet orifice. Who is correct?

• a. Technician A

• b. Technician B

• c. Both Technician A and Technician B

• d. Neither Technician A nor Technician B

Which of the following statements about Siemens CR injectors injection is NOT correct?

• a. When the piezoceramic actuator is energized by electrical current, the valve piston below the actuator transfers movement of the piezo stack to the mushroom valve

• b. This action opens the mushroom valve, causing fuel pressure in the control chamber to drain into the low-pressure fuel return circuit.

• c. Pressure below the nozzle valve is higher than the fuel pressure in the control chamber.

• d. The nozzle valve moves downward and injection begins.

Fuel drained from the Denso injectors is directed to the __________.

• a. Fuel filter

• b. Fuel tank

• c. Fuel injector inlet

• d. Fuel pump inlet

Technician A says piezoceramic actuators are more durable than servo-hydraulic actuators, which have greater wear rates. Technician B says because most heavy-duty engines do not commonly exceed 2500 RPM, the servo-hydraulic actuators are able to respond faster and with an adequate number of injection events. Who is correct?

• a. Technician A

• b. Technician B

• c. Both Technician A and Technician B

• d. Neither Technician A nor Technician B