Fuel Pressure Regulator: Testing and Inspection

FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING

Function
The fuel pressure regulator controls the fuel pressure dependent upon intake manifold pressure.

Special tools, testers and auxiliary items
- VAG 1318 pressure gauge
- VAG 1318/10 adapter
- VAG 1318/11 adapter
- VAG 1318/16 adapter

Test conditions
Fuel pump delivery rate OK.

WARNING! The fuel system is pressurized! Before loosening hose connections or opening the test connection, wrap a cloth around the connection. Then release pressure by carefully loosening and disconnecting the hose or fitting.

Test sequence





- Disconnect fuel supply hose -1- from fuel rail -2- and connect to VAG 1318 pressure gauge using VAG 1318/10 adapter.
- Connect VAG 1318 pressure gauge to fuel rail -2- using VAG 1318/11 and VAG 1318/16 adapters.
- Open gauge valve; handle in direction of flow (arrow)
- Start engine and run at idle speed.
- Check fuel pressure.

Specification: Approx. 2.5 bar (36 psi)





- Disconnect vacuum hose -1- from connection -2-.
- 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 residual pressure must be at least 2 bar (29 psi).

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







- After pressure has built up switch ignition off and at the same time close gauge valve; handle 90° to flow (arrow).
- Watch pressure drop on gauge.

If the pressure drops again:
- Check fuel pump check valve.

If the pressure does not drop:





- Open pressure gauge valve (arrow).
- Start engine and run at idle speed.
- After pressure has built up switch ignition off and at the same time clamp-off the return hose at fuel rail (blue arrow).

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

If the pressure continues to drop:
- Check VAG 1318 gauge, connections, fuel rail O-rings and fuel injectors for leaks.