With Generic Scan Tool

Fuel Pressure Regulator And Residual Pressure, Checking

The fuel pressure regulator controls the fuel pressure as a function of the Manifold Absolute Pressure (MAP).
The specified value for this test is dependent on the working pressure of the Fuel Pump (FP). This is about 4.0 bar positive pressure

Special tools and equipment







- VAG1318 pressure gauge







- VAG1318/6+7 adapter

WARNING: Fuel system is under pressure. Before opening system, place rags around the connection point. Then release pressure by carefully loosening connection.

Test sequence
I - Engine code AEB, ATW
II - Engine code AUG, AWM







- Open threaded connection (arrow) and absorb exiting fuel using a rag.







- Connect pressure gauge (VAG1318 using adapters VAG1318/6 and 1318/7) to supply line -1- and fuel distributor.
- Open shut-off valve of pressure gauge. The lever points in the direction of flow.
- Start engine and let run at idle.
- Measure fuel pressure.
Specified value: about 3.5 bar positive pressure







- Disconnect vacuum hose from fuel pressure regulator (arrow). Fuel pressure should rise to about 4.0 bar positive pressure.

NOTE: If fuel should escape at the vacuum connection of the pressure regulator, replace fuel pressure regulator

If specified value is not obtained:
- Delivery quantity of Fuel Pump (FP) OK, check, Fuel Pump (FP), checking.

If specified value is obtained:
- Switch ignition off.
- Now check for proper seal and residual pressure. Observe pressure drop on pressure gauge for this. After 10 minutes at least 2.0 bar positive pressure should still be present.

If residual pressure falls below 2 bar positive pressure:
- Start engine and let run at idle.







- Wait until pressure has risen, and then switch off ignition. Simultaneously close shut-off valve of pressure gauge (lever perpendicular to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.

If pressure does not drop:
- Test check valve of Fuel Pump (FP), Fuel Pump (FP), checking. Fuel Pump (FP), Checking

If pressure does drop again:
- Open stop valve of pressure gauge (lever in direction of flow -arrow-).
- Start engine and let run at idle.
- Wait until pressure has risen, and then switch off ignition. Simultaneously pinch return hose tightly together.

If pressure does drop again:
- Check whether pressure gauge is properly sealed.
- Check whether line connections, O-rings in fuel rail, and fuel injectors are properly sealed.

If no leaks are found:
- Replace fuel pressure regulator

NOTE: Before removing pressure gauge, put cleaning rags back around line connection which is to be disconnected.