Fuel Pressure: Testing and Inspection

System Pressure, Fuel Pressure Regulator and Residual Pressure, Checking

Special tools and equipment





- VAG 13/8
- VAG 1318/7





- VAG 1318/17 (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 conditions
- Fuel Pump (FP) OK, checking Testing and Inspection
- Fuel Pump (FP) OK, checking.
- Fuel filter OK
- Battery voltage at least 11 V

WARNING!
The fuel system is under pressure. When opening the system, place a rag around connections then release pressure by carefully prying open connection

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





- Remove fuel supply hose -1- (with white marking) from supply line.





- Connect VAG 1318 using adapters 1318/7 and 1318/17 (2 pieces) at supply line.
- Open 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 approx. 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.





- Switch ignition off after pressure has built up. Simultaneously close valve of VAG 1318 pressure gauge (lever perpendicular to direction of flow - arrow -).
- Observe pressure drop on pressure gauge.
- Check check - valve of Fuel Pump (FP).

If pressure drops again:
- Open valve of VAG 1318 pressure gauge (lever in direction of flow).
- Start engine and let run at idle.
- Switch ignition off after pressure has built up. Simultaneously clamp return line (with blue marking) fully closed (sealed).

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

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

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