With Manufacturer's Scan Tool

Fuel pressure regulator and residual pressure, checking


The fuel pressure regulator controls the fuel pressure as a function of the Manifold Absolute Pressure (MAP).

Special tools and equipment





- VAG 1318 pressure gauge
- VAG 1318/7 adapter
- VAG 1318/10 adapter
- VAG 1318/13 adapter

Test condition
- Capacity of transfer Fuel Pump (FP) must be OK, checking:

Test sequence

WARNING! Fuel system is under pressure! Before opening the fuel system, place rags under and around the connection then slowly release the fuel pressure.






- Unscrew fuel supply hose (1) from fuel rail (2).
- Connect pressure gauge VAG 1318 with adapters 1318/7, /10 and /13.
- Open shut-off valve of pressure gauge. The lever points in the direction of flow (arrow).
- Start engine and let run at idle.

- Measure fuel pressure.
Specification: about 3.5 bar positive pressure






- Pull vacuum hose off fuel pressure regulator (arrow).
Fuel pressure should rise to about 4.0 bar positive pressure overpressure.

NOTE: If fuel should escape at the vacuum connection of the pressure regulator, replace pressure regulator.

- Switch ignition off.
- Check for proper seal and residual pressure by observing pressure drop on pressure gauge.
After 10 minutes at least 2.2 bar overpressure should still be present.

If residual pressure falls below 2 bar overpressure:

- Start engine and let run at idle.






- Wait until pressure has dropped, and then switch off ignition. Simultaneously close stop valve of pressure gauge VAG 1318 (lever at right angles to direction of flow (arrow)).
- Observe pressure drop on manometer.

If pressure does not drop:

- Test check-valve on transfer Fuel Pump (FP).

If pressure does drop again:






- Open stop valve of pressure gauge VAG 1318 (lever in direction of flow (arrow)).
- Start engine and let run at idle.
- Wait until pressure has dropped, and then switch off ignition. Simultaneously pinch return hose (3) tightly together.

If pressure does not drop:
- Replace fuel pressure regulator item 5.

If pressure does drop again:
- Check whether line connections, O-rings in fuel rail, and fuel injectors are properly sealed.
- Check whether pressure gauge is properly sealed.

NOTE: Before removing pressure gauge, put cleaning rags back around line connection which is to be disconnected.