Checking Fuel Pressure (Low Pressure)

→ Ventilate the work area well.

→ Never ingest or inhale.

→ Read specific information on the Hazard Sheet.

→ Do not smoke, eat or drink in the work area.

→ Avoid contact with hot parts or sources of ignition.

→ Use suction to remove ignitable vapors.

→ Attach warning sign in a clearly visible position.

1. Checking Fuel Supply Pressure (Low Pressure) → 
   1. 1.1. Connect pressure gauge with stopcock tester K-Jetronic Tester VAG 1318 WE 1291  using adapter 1318/7 and connecting line Connection Line 9705/3  ("female" rapid-action coupling) on the side of the stopcock. On the other side of the stopcock, connect adapter 1318/15 (one-piece connecting piece) and connecting line Connection Line 9705/3  ("male" rapid-action coupling). The tool setup must be fitted with sealing rings (copper, aluminum, or plastic, etc.) between the individual components. The setup must be fully sealed. → Measuring tool for fuel delivery pressure 
      Fig 1: Measuring Fuel Delivery Pressure

      Courtesy of PORSCHE CARS NORTH AMERICA, INC.
      1. Connecting line Connection Line 9705/3  ("male" rapid-action coupling) → used for checking the fuel delivery pressure.
      2. Adapter 1318/15 (one-piece connecting piece); accessory for K-Jetronic Tester VAG 1318 WE 1291  ; → used for checking the fuel delivery pressure.
      3. Pressure gauge with stopcock tester K-Jetronic Tester VAG 1318 WE 1291 
      4. Adapter 1318/7 from K-Jetronic Tester VAG 1318 WE 1291 
      5. Connecting line Connection Line 9705/3  ("female" rapid-action coupling)
   2. 1.2. Connect measuring tool -2-  between the connection unit output -3-  and the fuel supply line -1-  . The stopcock is set to flow.
      Fig 2: Connecting Measuring Tool

      Courtesy of PORSCHE CARS NORTH AMERICA, INC.
   3. 1.3. Start the engine and leave it running at idle speed. Read off the fuel pressure on the pressure gauge. The pressure gauge pointer can oscillate slightly at idle speed. With increased idle speed (accelerator pressed slightly), the pointer deflection calms down. The fuel low-pressure system operates at a constant pressure of 5.5 to 6.0 bar  . The pointer oscillates at around this value. A measurement performed while driving by a second worker can also generate values of below 5 bar (4.5 bar) briefly at full throttle (with turbo in particular). This is not a sign of a defect.
2. Checking Fuel Retaining Pressure (Low Pressure) → 
   • Engine cold
   • Workshop air-conditioned to normal temperature
   • Fluctuations may occur if the engine is warm or the outside temperature is high
   • Fully sealed measuring tool setup
   1. 2.1. Same tool setup and connection as for measuring the fuel delivery pressure (see Fig 1).
   2. 2.2. Allow engine to run for a few minutes. Switch off engine. Check the pressure drop. Drop in fuel pressure after "ignition is switched off" must not exceed 1 bar  after 1 hour. Make sure that the tool setup itself does not have any leaks (even the slightest leak). The fuel retaining pressure will decrease extremely rapidly and falsify the measured result with even the tiniest leak.