System Pressure, Fuel Pressure Regulator and Holding Pressure, Checking

System Pressure, Fuel Pressure Regulator And Residual Pressure, Checking

Special tools and equipment







- VAG1318 Pressure gauge
- VAG1318/7 Adapter







- VAG1318/17 (2x) Adapter

NOTE: The fuel pressure regulator regulates fuel pressure according to the 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.

Requirements

- Fuel Pump (FP) Relay OK;
- Fuel Pump (FP) OK, checking:
- Fuel filter OK
- Battery voltage at least 12.7 V

WARNING: The fuel system is under pressure. Before opening the system, place rags around the connection. Then release pressure by carefully loosening the connection.

Checking system pressure







- Remove engine cover (arrows).







- Remove bolt -1- and remove reservoir cover (arrow).
- Open fuel filler flap briefly (pressure release).







- Disconnect fuel supply line -1- by pressing release button.







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







- Disconnect vacuum hose at fuel pressure regulator.
- 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 dropped, and then switch off ignition. Simultaneously 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 Fuel Pump (FP).

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

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

If pressure drops again:
- Check wiring connections, O-rings at fuel distributor and fuel injectors for proper seal.
- Check pressure gauge for proper seal.

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