Fuel Pressure: Testing and Inspection

Checking Fuel Pressure

Tools







Technical Values







Checking fuel pressure

INFORMATION:
- The battery voltage must not fall below 12 volts during the fuel pressure check.
- Connect a suitable battery charger.

1. Check the battery charging condition e.g. using a voltmeter or the Porsche PIWIS Tester. The battery voltage must not fall below 12 volts during the check.

WARNING:
Highly inflammable or explosive materials
- Danger of fire or explosion
- Avoid contact with hot parts or sources of ignition.
- Use suction to remove ignitable vapours.
- Attach warning sign in a clearly visible position.







2. Attach or mount a warning sign in a clearly visible position on the vehicle.
3. Relieve the fuel pressure.

WARNING:
Highly inflammable or explosive materials
- Danger of fire or explosion
- Avoid contact with hot parts or sources of ignition.
- Use suction to remove ignitable vapours.
- Attach warning sign in a clearly visible position.







4. Release metal cap on test connection at fuel collection pipe and screw it off by hand (a/f 13 mm). Collect emerging fuel with a cloth.







5. Connecting cable 9559 must be connected using the pressure gauge 378a (union nut a/f 17).







6. Tighten the knurled union nuts of the connecting cable by hand on the test connection of the fuel collection pipe -arrow-.

Procedure when engine is not running:

7. Connect the Porsche PIWIS Tester PIWIS Tester 9718 to the input socket in the vehicle using the adapter lead and switch on the ignition. Switch on the Tester and select the vehicle (option: Diagnostics).







8. Run the individual control unit search for DME using the Porsche PIWIS Tester. To do this, select DME with the tracer pen and press F12 >>.







9. Once the individual control unit search for DME is complete, select the Drive links item, then select the fuel pump relay and activate it by pressing F8 - Start.







10. Read value on pressure gauge. - Fuel pressure - engine not running: 3.8 bar±0.2 bar







11. Deactivate the fuel pump relay on the PIWIS Tester by pressing F8 - Stop. Then, press F11 << to return to the start screen and switch off the Tester.
12 Switch off the ignition and remove PIWIS Tester adapter lead in the vehicle.
13. To check the engine at idle speed: pressure gauge 378a must be connected as described above. Then start the engine. Switch off the engine after reading the fuel pressure. - Fuel pressure - idle speed: 3.8 bar±0.2 bar
14. Loosen the union nut on the connecting cable 9559 for the pressure gauge 378a on the test connection and remove special tool. Collect emerging fuel with a cloth.

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

15. Position new closure cap on test connection and tighten (a/f 13 mm). - Tightening torque: 2.5 Nm (2 ftlb.)±0.5 Nm (±0.5 ftlb.)