Fuel Pressure Sensor: Testing and Inspection

Fuel Pressure Sensor, Checking

Special tools, testers and auxiliary items required

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

• Assembly Tool (T10118)

• Pressure Sensor Tester (VAS 6394)

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

Procedure

CAUTION!
• The fuel pressure sensor is pressurized. Wear protective goggles and protective clothing to prevent injuries and contact with 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 (G247). Refer to => [ Fuel Pressure Sensor ] Service and Repair.

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





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





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





- Connect the (VAS 5570) to the fuel pressure sensor - 1 - and the electrical connector for the fuel pressure sensor.

- Install the engine cover/upper air filter housing and connect the Mass Airflow (MAF) sensor (G70).

- Turn the (VAS 6394/1) on by pressing the button - A - briefly.





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

• If the (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 vehicle's diagnostic connector.

- Turn on the ignition.

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

Vehicle Self Diagnosis

On Board Diagnostic (OBD) >

01 - Engine Electronics >

011 - Measured Values >

- Select the measured value block 1 4 0 and confirm with the Q button.

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

- Start the engine.

- Compare the pressure displayed by the (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.

CAUTION!
The (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 fuel pressure sensor to release the remaining pressure.

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

If the measured value do not match again:

- Perform a wiring test, refer to the vehicle diagnostic tester.