Fuel Pressure Regulator and Residual/Holding Pressure, Checking

Fuel Pressure Regulator And Residual Pressure

The fuel pressure regulator regulates the fuel pressure depending on intake manifold pressure.







Special tools, testers and auxiliary items required
- Pressure tester V.A.G 1318
- Adapter V.A.G 1318/9
- Adapter V.A.G 1318/17

Work sequence







- Remove fuse No. 28 (fuel pump) from fuse holder.

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







- Pull off supply line - 3 - and collect leaking fuel with a cloth.







- Connect pressure gauge V.A.G 1318 to fuel supply line and to hose to fuel rail using adapters V.A.G 1318/9 and V.A.G 1318/17.
- Open shut-off tap on pressure gauge. Lever points in direction of flow - arrow -.
- Reinstall fuse 28 (fuel pump) in fuse holder.
- Start engine and run at idling speed.
- Measure fuel pressure.
- Specification: approx. 2.5 bar

If the specification is obtained:







- Pull vacuum hose -1 - off fuel pressure regulator - 2 -.
- Fuel pressure must increase to approx. 3.0 bar
- Switch off ignition.

If the specification is not obtained:
- Check quantity supplied by fuel pump.

If the specification is obtained:
- Check for leaks and residual pressure by observing pressure drop on gauge.
- After 10 minutes, there must be a residual pressure of at least 2.0 bar.

If the holding pressure drops below 2 bar:
- Start engine and run at idling speed.







- Switch ignition off after pressure has built-up. At same time close shut-off tap of pressure gauge V.A.G 1318 (lever diagonal 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 shut-off tap of pressure gauge V.A.G 1318 (lever in direction of flow).
- Start engine and run at idling speed.
- Switch ignition off after pressure has built-up. At same time pinch/seal return hose closed.

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

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

NOTE: Before removing pressure tester, remove fuse 28 again and place a cloth around the connections to be loosened.