Fuel Pressure Sensor: Testing and Inspection

Fuel Pressure Sensor, Checking

Special tools, testers and auxiliary items required

• Assembly Tool (T10118)

• Double Hexagon Socket, 1/2, 27mm (VAS 5301/7)

• Pressure Sensor Tester (VAS 6394)

• Test Instrument Adapter/DSO (3-pin) (VAS 5570)

Procedure


• The fuel pressure sensor is under pressure. Always wear protective eyewear and protective clothing to prevent injuries and fuel from coming in contact with your skin. Wrap a cloth around the connection point before loosening the fuel pressure sensor. Then release pressure by carefully loosening.

- Remove the fuel pressure sensor. Refer to => [ Fuel Pressure Sensor (G247) ] Service and Repair.

- Remove the locking bolt - 2 - and install the fuel pressure sensor in the pressure sensor tester (VAS 6394/1). Tightening specification: 22 Nm.






- Coat the adapter (VAS 6294/2) sealing point with clean engine oil and install it in the fuel rail. Tightening specification: 22 Nm.






- Connect the pressure sensor tester (VAS 6394/1) pressure line to the adapter (VAS 6394/2).






- Connect the fuel pressure sensor - 1 - and the connector for the fuel pressure sensor using the test instrument adapter/DSO (3-pin) (VAS 5570).

- Reinstall the engine cover with air filter and connect the mass airflow sensor (G70).

- Press the button - A - once briefly to turn on the pressure sensor tester (VAS 6394/1).






• Holding the button - A - for 2 seconds switches on the illumination for 20 seconds.

• If the pressure sensor tester (VAS 6394/1) does not display 0 bar, set it back to zero. Refer to the operating instructions.

- Connect the vehicle diagnostic tester to the diagnostic connector.

- Turn on the ignition.

- Press the following buttons on the vehicle diagnostic tester screen one after another:

OBD

OBD ->

01 - engine electronics ->

011 - measured values ->

- Select the measured values block 1 4 0 and quit with Q.

Display field 3 shows the fuel pressure actual value as measured by the fuel pressure sensor.

- Start the engine.

- Compare the pressure displayed on pressure sensor tester (VAS 6394/1) with the actual value displayed on the vehicle diagnostic tester.

• The pressures may have a maximum difference of 5 bar.

- If the difference is greater than 5 bar, replace the fuel pressure sensor.


The pressure sensor tester (VAS 6394) is under high fuel pressure. Disconnect the connector from the fuel pressure sensor when the engine is running. This reduces the pressure to approximately 6 bar. Turn off the ignition. Place a cloth around the fuel pressure sensor , then carefully loosen the sensor to release the remaining pressure.

- Repeat the test with the new fuel pressure sensor and compare both values.

If the measured value do not match again:

- Check the wiring, refer to the vehicle diagnostic tester.