Fuel Tank: Service Precautions

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 a component in the fuel injection system high pressure area is remove, the fuel pressure must be definitely reduced to a residual pressure of approximately 6 bar, as described in the following.

Special tools, testers and auxiliary items required

• Trim Removal Wedge (3409)

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

Procedure

- With the ignition off, connect the Vehicle Diagnosis, Testing And Information System (VAS 5051B) to the Data Link Connector using the diagnostic lead.





- Start the engine and let it run at idle.

Display on (VAS 5051B):





- Press the Vehicle Self-Diagnosis button - 1 - in the selection.

Display on (VAS 5051B):





- In selection - 1 -, press "On Board Diagnostic (OBD)" and continue by pressing the -> button.

Display on (VAS 5051B):





- In selection - 1 -, press the "Engine electronics" vehicle system and continue by pressing the -> button.

Display on (VAS 5051B):





- In selection - 1 -, press the "Measured values" function and continue by pressing the -> button.

Display on (VAS 5051B):





- In selection - 1 -, press the "Fuel pressure" measured value and continue by pressing the -> button.

Display on (VAS 5051B):





- Check the display - 2 - for fuel pressure in the fuel rail.

• With the engine at idle, a value of approximately 35 kPa is displayed. This is the actual pressure in the fuel system generated by the high pressure pump.

• The unit "kPa" is also used instead of "bar": 1 bar = 1 kPA.

1. Control module identifications

- Pry the cover - 1 - on the left of the instrument panel off, for example using the Trim Removal Wedge (3409) - arrow -.





- Remove fuse 3 (SC3) (third from the top) in the driver side instrument panel fuse holder - ST2 - (brown).





Display on (VAS 5051B):





- With the engine still running, checking display - 2 - for the fuel pressure in the fuel rail:

• The fuel pressure decreases rapidly because the mechanical high pressure pump is no longer supplied with fuel by the electrical fuel pump.

- Switch the ignition off as soon as the fuel pressure drops just below 8 kPa.

• The fuel pressure must not drop below 6 bar or the engine will shut off (the catalytic converter could be damaged).

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 eyewear 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.

- Loosen the wire at a connection immediately.

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

Final procedures

- Insert fuse 3 (SC3) (third from the top) in the driver side instrument panel fuse holder - ST2 - (brown).





- If electrical connectors were disconnected and the engine was started, then malfunctions have been stored in the engine control module. "Generate readiness code" in "Guided Functions" Vehicle Diagnostic, Testing, And Information System (VAS 5051).