High-Pressure Fuel Injection System, Pressure Relief

High-Pressure Fuel Injection System, Pressure Relief

• The fuel injection system is separated into a high-pressure section (max. approximately 110 bar) and a low-pressure section (approximately 6 bar).

• Before opening the high-pressure section - e.g. removing the high-pressure pump, fuel rail, fuel injectors, the motor for intake manifold runner control valve or any other component or fuel line that is located in the high-pressure section of the fuel injection system - the fuel pressure in the high-pressure section must be relieved to a residual pressure of approximately 8 bar. The procedure for this is as follows.

Special tools, testers and auxiliary items required

• Vehicle diagnostic, testing and information system (VAS 5051) with diagnostic cable (VAS 5051/5A)

Work Procedure

- Start engine and run at idle speed.

- Connect vehicle diagnosis, testing and information system (VAS 5051) with diagnostic cable (VAS 5051/5A).





Display on (VAS 5051):





- Click on Vehicle Self-Diagnosis button.

Display on (VAS 5051):





- In selection - 1 -, press vehicle system "01 - Engine electronics".

- Wait until next display appears.

Display on (VAS 5051):





1 Control module identification of Engine Control Module (ECM)

- Click on -> button.

Display on (VAS 5051):





1 Selection of diagnostic functions

- In selection - 1 -, press diagnostic function "04- Basic Setting".

Display on (VAS 5051):





- Select "140" in button field - 2 - for "display group 140" and confirm input by pressing Q button.

Display on (VAS 5051):





Example:

1. 42%

2. 39.76 bar

3. 40.63 bar

4. Inactive

- Activate basic setting by pressing button A.





Display on (VAS 5051):

Example:

1. 0%

2. 0 bar

3. 5.46 bar

4. Lower

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

Now components or lines can be opened. A clean rag must be placed around connection points. Escaping fuel must be absorbed.

- In operating mode "Guided Fault-Finding", generate readiness code for Engine Control Module (ECM).