Fuel Pressure: Testing and Inspection

Fuel Pressure Regulator and Holding Pressure Check

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

Special tools and equipment







- VAG1318 Pressure gauge
- 1318/9 Adapter
- 1318/17 Adapter

Test sequence







- Remove fuse 28 (fuel pump) from fuse holder.


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







- Pull off supply pipe/hose -1- and collect leaking fuel with a cloth.







- Connect VAG1318 pressure gauge to fuel supply pipe/hose and to hose to fuel rail using adapters 1318/9 and 1318/17.
- Open shut-off tap on pressure gauge. The handle points in direction of flow.
- Refit fuse 28 (fuel pump) in fuse holder.
- Start the engine and run at idling speed.
- Measure fuel pressure. Specification: Approx. 2.5 bar







- Pull the vacuum hose -1- off fuel pressure regulator -2-. The fuel pressure must increase to approx. 3.0 bar.

If the specification is not obtained:
- Check quantity supplied by fuel pump.

If the specification is obtained:
- Switch ignition off.
- Check for leaks and holding pressure by observing pressure drop on gauge. After 10 minutes there must be a residual pressure of at least 2.0 bar.

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







- Switch ignition off after the pressure has built-up. At the same time close pressure measured device cut-off tap (handle cross through-flow direction -arrow-).
- Observe pressure drop on gauge.

If the pressure does not drop:
- Check fuel pump non-return valve.

If the pressure drops again:







- Open VAG1318 pressure tester shut-off tap (handle in through-flow direction).
- Start the engine and run at idling speed.
- Switch ignition off after the pressure has built-up. At the same time pinch/seal the return hose together.

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

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


NOTE: Before removing the pressure gauge, remove fuse 28 and place a cloth around the connections to be loosened.