Fuel System Overview (For Vehicles Through Fall 2009)

Fuel System Overview (for Vehicles through Fall 2009)

• Follow the guidelines for a clean working environment when working on the fuel system. Refer to => [ Clean Working Conditions ] Clean Working Conditions.

• Always follow these rules before and during work.

Follow the points below to avoid running the high pressure fuel pump dry (very low tolerances) and to start the engine quickly after replacing the components:

• If fuel system components between the fuel tank and high pressure fuel pump were removed or replaced, the fuel system must be bled. Refer to => [ Fuel System, Bleeding ] Fuel System, Bleeding.

• It is necessary to bleed the fuel system before starting the engine for the first time if the fuel pump, the fuel line (between the fuel tank and the fuel high pressure pump) or the fuel filter were removed.

• If the fuel high pressure pump was removed or replaced, then bleed the fuel system before starting the engine for the first time.

Fill the fuel tank after installing the high pressure pump. Refer to => [ Fuel Tank, Filling with Fuel after Installing High Pressure Pump ] General Information.

• If these instructions are not followed, the high pressure pump will be damaged during the first filling.






1 - Fuel Metering Valve (N290)

• Do not open

2 - High Pressure Pump

• After replacing, the fuel tank "must" be filled (never run dry), refer to => [ Fuel Tank, Filling with Fuel after Installing High Pressure Pump ] General Information

• The adaptation values must be adapted after replacing the high pressure pump or the fuel pressure regulator valve (N276) "Guided Functions" in the vehicle diagnostic tester.

• High pressure pump assembly overview, refer to => [ High Pressure Pump Overview ] Service and Repair

• Removing and installing, refer to => [ High Pressure Pump ] High Pressure Pump

3 - Fuel Rail

• Cylinder Bank 1

4 - Fuel Pressure Regulator Valve (N276)

• On cylinder bank 1

• Cannot be used again

• The adaptation values must be adapted after replacing the high pressure pump or the fuel pressure regulator valve "Guided Functions" in the vehicle diagnostic tester.

• Removing and installing, refer to => [ Fuel Pressure Regulator Valve (N276) ] Service and Repair

5 - Fuel Pressure Sensor (G247)

• On cylinder bank 2

• Removing and installing, refer to => [ Fuel Pressure Sensor (G247) ] Service and Repair

6 - Fuel Rail

• For cylinder bank 2

7 - Injector

• Removing and installing, refer to => [ Fuel Injectors ] Fuel Injectors

8 - Fuel Return Lines

• Do not disassemble the fuel return lines. Replace them completely with the pressure retention valve.

• Bleed the fuel system after replacing, refer to => [ Fuel Tank, Filling with Fuel after Installing High Pressure Pump ] General Information

9 - Pressure Retention Valve

• The check valve always maintains a residual pressure (control quantity) of approximately 10 bar (145 psi) in the fuel return lines.

• The Piezo injectors need this control quantity for their function.

• The check valve can be replaced only with the complete fuel return lines.

• Bleed the fuel system after replacing, refer to => [ Fuel Tank, Filling with Fuel after Installing High Pressure Pump ] General Information

• Check pressure retaining valve, refer to => [ Fuel Return Check Valve, Checking ] Fuel Return Check Valve, Checking

10 - Fuel Tank

• With transfer fuel pump (G6)

11 - Fuel Filter

12 - Auxiliary Fuel Pump (FP) (V393)

• The auxiliary FP is discontinued starting with MY 11.