Fuel Pressure: Testing and Inspection

Checking Fuel Pressure

WARNING: Observe the general safety instructions when working on the fuel system and when handling petrol and other fuels.
Attach or mount a warning notice on the vehicle in a clearly visible position.
Ensure good ventilation in the work area (e.g., open window, switch on exhauster).

Secure vehicle with warning sign.










NOTE: The battery voltage may not fall below 12 volts during the fuel pressure check.

1. Check the charge state of the battery, e.g. using a voltmeter or the Porsche System Tester PST 2. The battery voltage must not fall below 12 volts during the check.

NOTE: Use the brass closure cap on the test connection of the fuel pressure line only once as the sealing ring cannot be replaced. To avoid possible leaks, the cap must be replaced after removal.

2. Release the metal cap on the test connection of the pressure pipe from the fuel filter to the fuel collection pipe and screw it off by hand (a/f 13 mm).
3. Connect connecting lead 9559 with special tool pressure gauge P 378a (a/f 17 union nut) and manually attach the line to the test connection of the fuel supply line -arrow-.







Procedure when the engine is standing still:

4. Connect the Porsche Tester PST 2 in the vehicle, switch on the ignition and switch off all loads, such as the radio and air conditioning.
5. Activate fuel pump relay using Porsche System Tester. To do this, select the line drive links in the DME control unit individual search and then select fuel pump relay. Activate by pressing the F8 key.







6. Read value on pressure gauge.








Target test values when engine not running: 3.8 ± 0.2 bar.

7. Switch off the fuel pump relay on the System Tester by pressing F8.
8. Switch off ignition, pull off System Tester connecting lead in the vehicle and switch off System Tester.
Checking while engine is idling.

9. To check the engine while it is idling, connect the pressure gauge as described above and start the engine. Switch off the engine after reading the fuel pressure.
Target test values when engine is idling: 3.3 ± 0.2 bar.

10. Loosen the union nuts of the connecting cable 9559 for the special tool pressure gauge P 378a on the test connection and remove special tool. Collect emerging fuel, e.g. with a cloth.
11. Position new closure cap on test connection and tighten (a/f 13 mm).
Tightening torque of new brass closure cap: 2.5 ± 0.5 Nm ( 0.5 ftlb.)