Fuel Tank: Service Precautions

Before Opening High Pressure Fuel Injection System

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

Before opening high pressure components such as removing the high pressure pump, fuel rail, fuel injectors or fuel pipes, reduce the fuel pressure in the high pressure area to 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)

High fuel pressure, reducing

- Connect Vehicle Diagnostic, Testing, and Information System (VAS 5051B).





- 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 in 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 the Fuel Pump Control Module (J538) fuse in the fuse panel with the engine idling.





- Check 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 the ignition off as soon as the fuel pressure drops 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).

CAUTION!
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. To open fuel system, wear protective eye-wear and clothing to prevent injuries and contact with skin.

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.

Final procedures

- Re-install the Fuel Pump Control Module (J538) fuse.

- Erase the DTC memory and, using "Guided Fault Finding", generate the readiness code in the engine control module Vehicle Diagnosis, Testing and Information System (VAS 5051B).