Fuel Pressure Regulator: Testing and Inspection

The fuel pressure regulator regulates the fuel pressure relative to the intake manifold pressure.







The specified value for the check is dependent upon the working pressure of the fuel pump. This is approx. 3.0 bar.

Special tools and equipment
- VAG1318 pressure gauge
- 1318/10 adapter
- 1318/11 adapter
- 1318/16 hose adapter
- VAG1921 hose clip pliers

Test sequence







- Disconnect supply line/hose -1- and collect leaking fuel with a cloth.


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







- Connect VAG1318 pressure gauge using adapters VAG1318/10, /11 and /16.
- Open pressure gauge cut-off valve (handle points in direction of flow (arrow)).
- Start engine and run at idle.
- Check fuel pressure.
Specified value: approx. 2.5 bar

If the specified value is obtained:







- Disconnect vacuum line from fuel pressure regulator (arrow).

The fuel pressure must increase to approx. 3.0 bar.
- Switch ignition off.

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

If the specified value is obtained:
- 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.







- Switch ignition off after pressure has built-up. At the same time close pressure gauge cut-off valve (handle perpendicular to direction of flow (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 gauge shutoff tap (handle perpendicular to direction of flow).
- Start engine and run at idle.
- Switch ignition off after pressure has built-up. At same time pinch/seal return line together.

If the pressure does not drop:
- Replace fuel pressure regulator, item -15-. Refer to "Intake Manifold Lower Section, Disassembling and Assembling",

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


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