With Manufacturer's Scan Tool

System Pressure, Fuel Pressure Regulator And Holding Pressure, Checking

Special tools and equipment






- VAG 1318
- VAG 1318/7






- VAG 1318/17 (2x)

NOTE: The fuel pressure regulator regulates the fuel pressure according to the intake manifold pressure. This ensures that the drop in pressure at the injectors remains the same throughout all engine speed and engine load ranges.

Requirements for test:
- Fuel pump relay OK.
- Fuel pump OK.
- Fuel filter OK
- Battery voltage not less than 12.7 V

WARNING: Fuel system is under pressure. Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

Testing system pressure






- Remove engine cover panel -1- -arrows-.
- Briefly open fuel tank filler cap (to release pressure).






- Press release catch and disconnect fuel supply pipe -1-.






- Connect pressure gauge VAG 1318 to fuel supply pipe using adapters 1318/7 and 1318/17 (x 2).
- Open cut-off valve on pressure gauge (valve handle points in direction of flow).
- Start the engine and run at idling speed.
- Measure fuel pressure.
- Specification: approx. 2.5 bar






- Disconnect vacuum hose from fuel pressure regulator.
- The fuel pressure should rise to approx. 3.0 bar.
- Switch off ignition.
- Check leak-tightness and holding pressure by watching the drop in pressure on the pressure gauge.
- After 10 minutes there should still be a pressure of at least 1.5 bar.

If the holding pressure drops below 1.5 bar:
- Start the engine and run at idling speed.






- Allow pressure to build up, then switch off ignition and at the same time close cut-off valve on pressure gauge VAG 1318 (valve handle at right angles to direction of flow -arrow-).
- Observe pressure drop on gauge.

If the pressure does not drop:
- Check fuel pump non-return valve.

If the pressure drops again:
- Open cut-off valve on pressure gauge VAG 1318 (valve handle points in direction of flow).
- Start the engine and run at idling speed.
- Allow the pressure to build up, then switch off the ignition. At the same time pinch the return hose (with blue marking) firmly together.

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

If the pressure drops again:
- Check pipe connections, O-rings on fuel manifold and injectors for leaks.
- Check pressure gauge for leaks.

NOTE: Before removing the pressure gauge, release the fuel pressure by opening the cut-off valve.When doing this, hold a container over the connection.