Pressure Retention Valve in Fuel Return Line, Checking

Pressure Retention Valve in Fuel Return Line, Checking

Function

The pressure retention valve in the fuel return line 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


• Follow the safety precautions when working on the diesel direct injection system. Refer to => [ Safety Precautions ] Diesel Fuel Injection.

• Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Diesel Fuel Injection.

Always follow these instructions before and during work.

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

- Remove the protective strip - item 1 - in the => [ Fuel Rail and Injectors Overview ] Service and Repair, if equipped.

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

- Dry the cylinder 1 return line connection.

- Cover the cylinder 1 return line connection with a cloth.

- Remove the fuel return line connection from cylinder 1. Pull it upward to release it - arrow -.






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

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






- Start the engine and run at idle speed.

- Check the pressure on the tester for fuel return system.

• Specified value: approximately 10 bar

If the specification is not obtained:

- Replace the pressure retention valve - item 8 - in the => [ System Overview ] Removal and Replacement.