Fuel Pressure Regulator: Testing and Inspection

Residual Pressure and Fuel Pressure Regulator, Checking

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required







- VAG 1318 Pressure gauge
- VAG 1318/10 Adapter
- VAG 1318/11 Adapter
- VAG 1318/16 Hose adapter
- VAS 5024 Assembly tool for spring-type clips

Function
The fuel pressure regulator regulates the fuel pressure depending on intake manifold pressure.
The specification for the check is dependent upon the working pressure of the fuel pump. This is Approx. 3.0 bar

Test prerequisites
- Fuel pump delivery rate OK., checking:

Test sequence







- Pull fuse No. 28 (for fuel pump) out of fuse holder.







- Pull fuel supply hose -1- (black) off fuel rail and collect fuel that leaks out 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 pressure gauge VAG 1318 with adapter, VAG 1318/10 to supply hose -1- and with adapter VAG 1318/11 and VAG 1318/16 hose adapter to supply line.
- Open shut-off tap on pressure gauge. The handle points in throughflow direction -arrow-.
- Install fuel pump fuse No. 28 into fuse holder.
- Start engine and run at idle.
- Measure fuel pressure.
Specification: Approx. 2.5 bar







- Pull vacuum hose off fuel pressure regulator -arrow-. The fuel pressure must increase to approx. 3.0 bar.
- Switch off ignition.

If the specification is not obtained:
- Check delivery rate of fuel pump:

If the specification is obtained:
- Now check for leaks and holding pressure.Watch 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.

When the fuel pump has built up the pressure again:







- Switch ignition off after the pressure has built-up. At the same time close pressure gauge VAG 1318 cut-off tap (handle cross through-flow direction -arrow-).
- Watch pressure drop on gauge again.

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

If the pressure drops again:







- Open pressure gauge VAG 1318 shut-off tap (handle in direction of flow -arrow-).
- Start engine and run at idle speed.







- Switch ignition off after the pressure has built-up. At the same time clamp-off the return supply hose (with blue marking) -2-.
- Switch off ignition.

If the pressure does not drop:
- Replace fuel pressure regulator, item 11.

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

When the pressure gauge is removed after completing the test:
- Remove fuse No. 28 from fuse holder again before removing pressure gauge and place a cloth around the connections to be loosened.