Fuel Injection System

Before Opening High Pressure Fuel Injection System


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

Special tools, testers and auxiliary items required

• Vehicle Diagnostic, Testing, and Information System (VAS 5051B)

Procedure

- Connect the vehicle diagnosis tester.






- Start engine and run at idle speed.

- Select "Engine Electronics" in OBD.

- Then select "Measured Values" read out.

- Select measured value block 140.

- With the engine running at idle, the fuel pressure will be displayed in display field 3.

• Specified value: between 35 and 45 bar.

- Remove the right instrument panel cover.

- Remove fuse 1 in the fuse carrier ST2 (brown) - 2 -.






• Ignore - 1 and 3 -.

- Follow the fuel pressure on the tester.

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

- Switch 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.

• Wear protective eye-wear and clothing when opening the fuel system.

• Lay clean cloths around the connection before opening the high pressure area to collect any fuel that leaks out.

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

Final Procedures

- Install fuse 1 in the fuse carrier ST2 (brown).

- Install the right instrument panel cover.

- Erase the DTC memory and generate the readiness code in the engine control module in "Guided Functions".