Fuel Pressure Check Valve: Testing and Inspection

Pressure Retention Valve in Fuel Return Line, Checking

Function

The pressure retaining valve in the fuel return maintains a residual pressure (control quantity) of approximately 10 bar.

The fuel injectors require this control quantity to function correctly.

Special tools, testers and auxiliary items required

• Tester for fuel return system (VAS 6330)

Test Sequence

CAUTION!
• Follow the safety precautions when working on the diesel direct injection system. Refer to --> [ Safety Precautions ] Safety Precautions.

• Observe rules for cleanliness. Refer to --> [ Clean Working Conditions ] Clean Working Conditions.

Always follow these instructions before and during work.

- Remove engine cover. Refer to --> [ Engine Cover ] Engine Cover.

- Remove protective strip --> [ 1 Protective Strip ] Removal and Replacement.

- Before removing, clean the cylinder 1 return line connection (for example using a commercially available detergent).

- Dry cylinder 1 return line connection.

- Cover cylinder 1 return line connection with a rag.

- Remove cylinder 1 fuel connection. Pull them upward to release them - arrow -.





• Maintain clean working conditions. Dirt and contaminants must not enter the return line and the connection on the fuel injectors.

- Install tester for fuel return system (VAS 6330) between return line connection on the fuel injector and the return line.





- Start engine and run at idle speed.

- Check pressure on the tester for fuel return system.

• Specified value: approximately 10 bar

If specification is not obtained, replace pressure retaining valve --> [ 8 Pressure Retention Valve ] [1][2]Diagrams.