With Manufacturer's Scan Tool

Fuel Pressure Regulator And Holding Pressure, Checking

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

Special tools, test equipment and auxiliary items





- VAG 1318 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 line/hose -1- and collect leaking fuel with a cloth.






- Connect VAG 1318 pressure gauge to fuel supply line/hose and to hose to fuel rail using adapters 1318/9 and 1318/17.
- Open measured device cut-off tap. (Handle points in through-flow direction -arrow-).
- Refit fuse 28 (fuel pump) in fuse holder.
- Start engine and run at idle speed.
- Measure fuel pressure.

Specification: Approx. 2.5 bar

If the specification is obtained:






- Pull vacuum hose -1- off fuel pressure regulator -2-.
Fuel pressure must increase to approx. 3.0 bar.
- Switch off ignition.

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

If the specification is obtained:
- Switch off ignition.
- 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 engine and run at idle speed.






- Switch ignition off after pressure has built-up. At 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 VAG 1318 pressure gauge shut-off tap (handle in through-flow direction).
- Start engine and run at idle speed.
- Switch ignition off after pressure has built-up. At same time pinch/seal return hose together.

If the pressure does not drop:
- Replace fuel pressure regulator, item 4.

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