Fuel Return Line Pressure Retention Valve, Checking

Fuel Return Line Pressure Retention Valve, Checking

In vehicles equipped with a 6 bar (87 psi) fuel system, the pressure retention valve function in the fuel return line is to guarantee a constant residual pressure (control quantity). The injectors need this control quantity to function correctly.

Special tools, testers and auxiliary items required

• Tester for Fuel Return System (6330)

• 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 => [ Engine Cover ] Engine Cover.

- Before removing, clean the cylinder 1 return line connection using for example 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 the first cylinder. Press the connection downward and pull the center piece upward.

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

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






- Start the engine.

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

• Specified value: approximately 4 bar (58 psi)

If the target value is not reached, replace the fuel return line, including the pressure retention valve.