Fuel Delivery and Air Induction

Diesel Direct Injection System Assembly Overview

CAUTION!
• Follow the safety precautions when working on the diesel direct injection system. Refer to --> [ Safety Precautions ] Safety Precautions.

• Observe rules for cleanliness. Refer to --> [ Clean Working Conditions ] Clean Working Conditions.

Always follow these instructions before and during work.





1 Fuel Metering Valve (N290)

• Do not open

2 Fuel High Pressure Pump

• Removing and installing, refer to --> [ High Pressure Fuel Pump ] High Pressure Fuel Pump.

• The fuel system must always be filled after replacing (never run dry) --> [ Fuel System, Filling ] Fuel System, Filling.

3 Fuel Pressure Sensor (G247)

• Removing and installing, refer to --> [ Fuel Pressure Sensor ] Service and Repair.

4 Rail Element (High Pressure Reservoir)

5 Fuel Pressure Regulator Valve (N276)

• Removing and installing, refer to --> [ Fuel Pressure Regulator Valve ] Service and Repair.

6 Injection Unit (Piezo Injector)

• Removing and installing, refer to --> [ Fuel Injection Unit ] Service and Repair.

7 Fuel Return Lines

• Do not disassemble fuel return lines. They can only be replaced completely with the pressure retaining valve --> [ 8 Pressure Retention Valve ].

• After replacing, run the engine at idle for approximately 2 minutes to bleed the fuel system, then check the fuel return lines for leaks.

8 Pressure Retention Valve

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

• The fuel injectors require this control quantity to function correctly.

• The pressure retaining valve can only be replaced completely with the fuel return lines --> [ 7 Fuel Return Lines ]

• After replacing, the engine must run at idle for approximately 2 minutes to bleed the fuel system.

• Checking, refer to --> [ Pressure Retention Valve in Fuel Return Line, Checking ] Testing and Inspection

9 Fuel Tank

• Refer to --> [ Fuel Tank Assembly Overview ] Fuel Tank Assembly Overview

10 Fuel Filter

• Refer to --> [ Fuel Filter Assembly Overview ] Fuel Filter Assembly Overview

11 Auxiliary Fuel Pump (V393)

• Removing and installing, refer to --> [ Auxiliary Fuel Pump ] Auxiliary Fuel Pump