Fuel Pressure Check Valve: Testing and Inspection

Fuel Return Check Valve, Checking

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

The fuel injectors need this control quantity to function correctly.

Special tools, testers and auxiliary items required

• Tester for Fuel Return System (VAS 6330)

CAUTION!
• Follow the guidelines for a clean working environment when working on the fuel system. Refer to => [ Clean Working Conditions and Fuel System Work Instructions ] Clean Working Conditions and Fuel System Work Instructions.

• Always follow these rules before and during work.

- Remove the engine cover. Refer to => [ Remove the engine cover. First
pull the cover forward and then pull it upward ] Engine, Removing.

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

- Dry the cylinder 1 return line connection.

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

- Remove the return line connection on the first cylinder. Press the connection at the tabs downward and pull the center piece upward to release it.

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

- Install the (VAS 6330) between the return line connection on the injector and the return line.





- Start the engine.

- Check the pressure on the (VAS 6330) for fuel return system.

• Target value: approximately 10 bar

If the specified value is not reached, replace the check valve.