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).

Recommended special tools and equipment
- VAG1318 pressure gauge
- Adapter 1318/9
- Adapter 1318/17

Test sequence





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


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






- Disconnect supply line -1- and catch escaping fuel using a rag.






- Connect pressure gauge (VAG1318 using adapters VAG1318/9 and 1318/17) to supply line and hose for fuel distributor.
- Open shut-off valve of pressure gauge. The lever points in the direction of flow.
- Re-insert fuse 28 (fuel pump) in fuse holder.
- Start engine and let run at idle.
- Measure fuel pressure.
Specified value: approx. 2.5 bar positive pressure






- Disconnect vacuum hose -1- from fuel pressure regulator -2-. Fuel pressure should rise to approx. 3.0 bar positive pressure rise.

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.

If pressure does drop again:






- Open shut-off valve of pressure gauge (VAG1318) (lever in direction of flow).
- 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 not drop:
- Replace fuel pressure regulator, item 12

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

NOTE: Before removing pressure gauge, remove fuse 28 again and put cleaning rags back around line connection which is to be disconnected.