Fuel Return Line Pressure Retention Valve, Checking

Fuel Return Line Pressure Retention Valve, Checking

The pressure retention valve in the fuel return lines maintains a residual pressure 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)


• Follow the guidelines when working on the fuel system. Refer to => [ Safety Precautions ] Safety Precautions.

• Follow the guidelines for clean working conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions.

• Always follow these rules before and during work.

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

- Before removing, clean the cylinder 1 return line connection 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 from cylinder 1. Press the connection downward and pull the center piece upward.

• Pay attention to cleanliness. Dirt and contaminants must not get into the return lines and the connections on the fuel injectors.

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






- Start the engine.

- Let the engine idle until the pressure gauge is completely ventilated.

• The pressure gauge line must be completely bled in order to perform the test. The bleeding procedure is complete once all of the air bubbles are removed from the transparent connection block.

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

• Specified value: 8 to 14 bar

If the Specification is not Obtained

- Replace the pressure retention valve.

If the specification is Obtained

- Shut off the engine. The pressure indicator value on the pressure gauge must remain constant.

If the Pressure Indicator Value Decreases

- Replace the pressure retention valve.