Fuel Pressure: Testing and Inspection

Fuel Pressure Regulator and Residual Pressure, Checking:

The fuel pressure regulator controls the fuel pressure relative to Manifold Absolute Pressure.

Special tools, testers and auxiliary items:

- VAG 1318 pressure tester.
- VAG 1318/10 adapter.
- VAG 1318/11 adapter.
- VAG 1318/16 adapter.

Test conditions:

- Fuel pump delivery rate OK.

Test sequence:

Note:To prevent fuel spray when loosening hose connections, wrap a cloth around the connection.






- Remove fuel rail plug -1- from fuel rail and connect pressure gauge VAG 1318 with adapter VAG 1318/10 and hose VAG 1318/1 to fuel rail. the shut-off lever on the pressure gauge must be closed (lever -arrow- at right angles to direction of flow)
- Start engine and let idle.

- Check fuel pressure.
Specification: Approx. 2.5 bar (36 psi).






- Pull vacuum hose off fuel pressure regulator on intake manifold upper part -arrow-. The fuel pressure must rise to approx. 3.0 bar (44 psi).

- Switch ignition off.
- Check for leaks and residual pressure by watching pressure drop on gauge.
- After 10 minutes there must be a residual pressure of at least 2.0 bar (29 psi).

If the residual pressure drops below 2.0 bar (29 psi):

- Start engine and let idle.
- After the pressure has built up switch ignition off and at the same time clamp-off return line (with blue markings) on fuel rail.
- Watch pressure drop on gauge.

If the pressure does not drop:

- Replace fuel pressure regulator.

If the pressure drops again:

- Check fuel pump check valve.
- Check hose connections, O-rings on fuel rail and fuel injectors for leaks.
- Check pressure gauge for leaks.