System Pressure, Fuel Pressure Regulator and Holding Pressure

System Pressure, Fuel Pressure Regulator And Residual Pressure, Checking

Special tools and equipment






- VAG1318
- VAG1318/7






- VAG1318/17 (2x)

NOTE: Fuel pressure regulator regulates fuel pressure according to intake manifold pressure. This ensures that the pressure drop at the fuel injectors remains the same for each speed and load range of the engine.

Test requirements:
- Fuel Pump (FP) OK, checking. Fuel Pump (Fp) Relay -J17-, Testing and Activating
- Fuel Pump (FP) OK, checking:
- Fuel filter OK
- Battery voltage at least 11 V

WARNING: Fuel system is under pressure! Place a cloth around connection point before opening system. Then release pressure by carefully loosening connection point.

Checking system pressure
- Open fuel filler flap briefly (pressure release).






- Remove fuel supply hose -1- (with white marking) from supply line, press release button for this.






- Connect VAG1318 using adapters 1318/7 and 1318/17 (2 pieces) at supply line.
- Open shut-off valve of pressure gauge. The lever points in the direction of flow.
- Start engine and let run at idle.
- Measure fuel pressure.
- Specification: about 2.5 bar positive pressure






- Disconnect vacuum hose at fuel pressure regulator (arrow).
- Fuel pressure must rise to about 3.0 bar positive pressure.
- Switch ignition off.
- Check for proper seal and residual pressure by observing pressure drop on pressure gauge.
- After 10 minutes, there must be at least 1.5 bar positive pressure

If residual pressure sinks below 1.5 bar positive pressure:
- Start engine and let run at idle.






- Wait until pressure has built up, and then switch off ignition. Immediately close shut-off valve of VAG1318 pressure gauge (lever perpendicular to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.

If pressure does not drop now:
- Test check-valve on transfer Fuel Pump (FP).

If pressure drops again:
- Open shut-off valve of VAG1318 pressure gauge (lever in direction of flow -arrow-).
- Start engine and let run at idle.
- Wait until pressure has built up, and then switch off ignition. Then immediately clamp return line (with blue marking) completely closed.

If pressure does not drop now:
- Replace fuel pressure regulator

If pressure drops again:
- Check wire connections, O-rings at fuel rail and fuel injectors for proper seal.
- Check whether pressure gauge is properly sealed.

NOTE: Before disconnecting pressure gauge, release pressure by opening shut-off valve. Hold a container in front of connection for this.