Checking Fuel Pressure

Information

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

Check the battery charge state 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 vapors.

→ Attach warning sign in a clearly visible position.
Attach or mount a warning sign in a clearly visible position on the vehicle.

Fig 1: Example Of Warning Sign
Courtesy of PORSCHE CARS NORTH AMERICA, INC.

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.
Release metal cap on test connection at the fuel collection pipe -arrow- and screw it off by hand (a/f 13 mm).

Fig 2: Locating Metal Cap On Fuel Collection Pipe
Courtesy of PORSCHE CARS NORTH AMERICA, INC.
Connecting cable 9559 must be connected using special tool pressure gauge 378a (union nut a/f 17).
- A - Connection line (9559)
- B - Pressure gauge (378a)
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 vapors.

→ Attach warning sign in a clearly visible position.
Tighten the knurled union nuts of the connecting cable by hand on the test connection of the fuel collection pipe -arrow- . Soak up emerging fuel with a cloth.

Fig 4: Locating Pressure Gauge To Fuel Collection Pipe Knurled Union Nut
Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Procedure when the engine is standing still:
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).
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 >>].

Fig 5: Display - Control Unit Search Screen
Courtesy of PORSCHE CARS NORTH AMERICA, INC.
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.

Fig 6: Display - Activating Drive Link Screen (For Fuel Pump Relay)
Courtesy of PORSCHE CARS NORTH AMERICA, INC.
Read value on pressure gauge. → Fuel pressure - engine not running: 3.8 bar+/-0.2 bar
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.

Fig 7: Display - Deactivating Drive Link (For Fuel Pump Relay)
Courtesy of PORSCHE CARS NORTH AMERICA, INC.
Switch off the ignition and remove PIWIS Tester adapter lead in the vehicle.
Checking the engine at idle speed: connect the pressure gauge 378a as described above and start the engine. Switch off the engine after reading the fuel pressure. → Fuel pressure - idle speed: 3.8 bar+/-0.2 bar
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 vapors.

→ Attach warning sign in a clearly visible position.
Loosen the union nut on the connecting cable 9559 for the pressure gauge 378a on the test connection and remove special tool. Soak up 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.
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.)