Releasing Pressure In High Pressure Area

Releasing Pressure in High Pressure Area

• The fuel injection system is separated into a high-pressure section (maximum approximately 120 bar) and a low-pressure section (approximately 6 bar).

• Before opening the high pressure area, fuel pressure must be reduced to a residual pressure of approximately 6 bar. The procedure for this is as follows.

High Fuel Pressure, Reducing

- Connect a vehicle diagnosis tester.

- Start engine and run at idle speed.

- Select "engine electronics" in OBD.

- Then select "Measured values".

- Select "Fuel pressure" from the list.

• Specified value: between 35 and 45 bar

- Pry the cover - 1 - on the left and right of the instrument panel off, for example using the trim removal wedge (3409) - arrow -.






- While the engine is idling, remove the fuse - in the fuse holder inside the instrument panel on the driver side - from the Fuel Pump (FP) control module (J538).






• By removing fuse, the voltage supply to terminal 30 for the FP Control Module is interrupted.

- Check the fuel pressure displayed.

• The fuel pressure decreases rapidly because the mechanical high pressure pump is no longer supplied with fuel from the transfer fuel pump (G6).

- Turn off the ignition as soon as the fuel pressure has decreased to approximately 8 bar.

• The fuel pressure must not drop below 6 bar, because otherwise the engine will shut off (risk of catalytic converter damage).

The fuel rail will continue to be filled with fuel, but it will no longer be under high pressure.

Do not let fuel come into contact with skin.

• The fuel lines will continue to be filled with fuel, but will no longer be under high pressure. Wear protective goggles and protective clothing when opening the fuel system.

• Before opening the high pressure system, place a cloth around the connection.

- After reducing fuel pressure, place a clean cloth around the connection and open the high pressure system immediately. Escaping fuel must be absorbed.

• If the high pressure system is not opened immediately, the pressure will increase because of post-heating.

- Lay clean cloths around connectors and catch escaping fuel.

Final Procedures

- Install the fuse.

- Install the instrument panel cover..

- Erase the Diagnostic Trouble Code (DTC) memory and generate the readiness code in the Engine Control Module (ECM) in "Guided Functions".