Fuel Pressure Regulator and Residual Pressure, Checking

Residual pressure and fuel pressure regulator, checking

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

Special tools, testers, measuring instruments and auxiliary items required

- VAG 1318 Pressure tester
- 1318/6 adaptor
- 1318/7 adaptor


WARNING!
Fire hazard! Do not have anything in area that can ignite fuel!

Test conditions
- Fuel pump delivery rate OK

Test sequence


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

- Open the union -arrow- and catch escaping fuel with a cloth.







- Connect pressure gauge VAG 1318 to fuel supply pipe -1- and to fuel rail using adaptors 1318/6 and 1318/7.






- Open shut-off tap on pressure gauge.
- Handle points in direction of flow
- Start the engine and run at idling speed.
- Measure fuel pressure.
- Specification: Approx. 3.5 bar

If specification obtained

- Disconnect the vacuum hose off fuel pressure regulator -arrow-







- Fuel pressure must increase to approx. 4.0 bar
- Switch OFF ignition.
- Check for leakage and residual pressure by observing pressure drop on gauge.
- After 10 minutes residual pressure must be 2.0 bar minimum

If the holding pressure drops below 2 bar:

- Start engine and let idle.
- Switch OFF ignition after pressure has built- up, at same time close pressure tap







- VAG 1318 handle perpindicular to direction of flow -arrow-
- Observe pressure drop on gauge.

If pressure does not drop:
- Check fuel pump check valve.

If pressure drops again

- Open pressure tester VAG 1318 shut-off tap.







- VAG 1318 handle in direction of flow
- Start engine and let idle.
- Switch OFF ignition after pressure has built- up, at same time pinch/seal return hose.

If pressure does not drop

- Replace fuel pressure regulator If pressure drops again
- Check line connections, O-rings on fuel manifold and fuel injectors for leakage.
- Check pressure gauge for leaks.


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