Fuel Pressure Sensor: Testing and Inspection

Fuel Pressure Sensor, Checking

Special tools, testers and auxiliary items required

• Assembly Tool (T10118)

• Torque Wrench (5-50 Nm) (V.A.G 1331)

• Vehicle Diagnostic Tester

• Pressure Sensor Tester (VAS 6394/1) with Adapter (VAS 6394/2)

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

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

Test Sequence

• Refer to => [ Fuel Rail and Injectors Overview ] Fuel Rail and Injectors Overview.

- Read the safety precautions before starting. Refer to => [ Safety Precautions ] Safety Precautions.

- Pay attention to the rules of cleanliness. Refer to => [ Clean Working Conditions ] Clean Working Conditions.

The fuel system is under pressure!

• Before opening the high pressure side components, the fuel pressure must be relieved to residual pressure. Refer to => [ High Side Fuel Pressure, Releasing ] Service and Repair.

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

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

- Coat the adapter (VAS 6394/2) sealing point with clean engine oil and install it in the fuel rail.






Tightening specification: 27 Nm

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






Tightening specification: 27 Nm

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

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






- Switch the pressure sensor tester (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 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 - 1 - as follows:






- Connect the diagnostic cable - 2 - to the Data Link Connector (DLC) in the drivers foot well.

- Turn the ignition on.

- On the following screens, select:

OBD

01 - engine electronics ->

011 - measured values ->

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

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

- Start the engine and let run at idle.

- Compare the pressure displayed by the 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.

The pressure sensor tester (VAS 6394/1) 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.

Difference greater than 5 bar:

- Replace the fuel pressure sensor.

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

If the measured value do not match again:

- Check the wiring using "Guided Fault Finding" in the vehicle diagnostic tester.