Fuel Pressure: Testing and Inspection

Fuel Pressure Regulator and Residual Pressure, Checking:

The fuel pressure regulator controls the fuel pressure dependent upon intake manifold 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:


WARNING: DO NOT smoke or work near heaters or other fire hazards when working on fuel system.
The fuel system is pressurized! Before loosening hose connections or opening the test connection, wrap a cloth around the connection. Then release pressure by slowly disconnecting the hose/fitting






- Disconnect test port plug -1- from fuel rail and connect pressure gauge VAG 1318 with adapter VAG 1318/10 and hose VAG 1318/1 to fuel rail.
- Fuel gauge valve must be closed, handle 90° to direction of flow (arrow).
- Start engine and run at idle speed.
- Check fuel pressure.
Specification: approx. 2.5 bar (36 psi).






- Disconnect vacuum hose from intake manifold upper section at fuel pressure regulator (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 bar (29 psi).

If the residual pressure drops below 2 bar (29 psi):

- Start engine and run at idle speed.
- After the pressure has built up switch ignition off and at the same time clamp-off return line (with blue arrow) 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.