Fuel Pressure: Testing and Inspection

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

Test conditions:
- Fuel pump delivery rate OK

WARNING!
- Fire Hazard! Do NOT have anything in area that can ignite fuel!
- Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.





Test sequence:
- 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 perpendicular 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.