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

Test conditions
- Fuel pump delivery rate OK, checking:

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 fuel supply line -1- from fuel rail -2- and connect using adapter 1318/10 to pressure tester VAG 1318.
- Connect pressure tester VAG 1318 to fuel rail -2- using adapter 1318/11 and 1318/16. Open pressure tester shut-off valve, handle in direction of flow (arrow).
- Start engine and run at idle speed.
- Check fuel pressure.

Specification: approx. 2.5 bar (36.3 psi)





- Disconnect vacuum hose -1- from connection -2-.

- The fuel pressure must rise to approx. 3.0 bar (43 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 close pressure tester VAG 1318 shut-off valve, handle 90° to direction of 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 tester VAG 1318 shut-off valve, handle in direction of flow (arrow).
- Start engine and run at idle speed.
- After the pressure has built up switch ignition off and at the same time clamp-off the return line (with blue arrow) on fuel rail.

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

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