With Generic Scan Tool

Fuel Pressure Regulator And Residual Pressure, Checking

Function

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 approx.. 3.0 bar positive pressure

Recommended special tools and equipment

Vehicles with engine code AEG, AVH, AZG
- V.A.G 1318 pressure gauge
- VAG 1318/10 adapter
- VAG 1318/11 adapter
- VAG 1318/16 hose adapter
- VAS 5024 assembly tool for spring-type clamps

Vehicles with engine code BDC

- V.A.G 1318 pressure gauge
- VAG 1318/9 adapter
- VAG 1318/17 adapter

Test requirements

- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in position -P- or -N-.
- Delivery quantity of Fuel Pump (FP) OK. Testing and Inspection

Test sequence (Vehicles with engine code AEG, AVH, AZG)

- Remove fuse 28 from fuse holder.

NOTE: By removing fuse 28, the voltage supply for the Fuel Pump (FP) is interrupted for safety reasons, otherwise the Fuel Pump (FP) would start up when the driver's door is opened.

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

- Disconnect fuel supply line -1- (black) from fuel distributor and catch escaping fuel using a rag.

- Connect pressure gauge to adapter (VAG 1318/10) at supply hose and to adapter (VAG 1318/11) and hose adapter (VAG 1318/16) at supply line.
- Open shut-off valve of pressure gauge. The lever points in the direction of flow (arrow).
- 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 connecting piece -2-. Fuel pressure should rise to approx.. 3.0 bar positive pressure rise.

NOTE: If fuel should escape at the vacuum connection of the pressure regulator, replace fuel pressure regulator, item 1.

- 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). Testing and Inspection

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 not drop:
- Replace fuel pressure regulator, item 1.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If pressure does drop again:
- Check whether line connections, O-rings in fuel distributor, and fuel injectors are properly sealed.
- Check pressure gauge for proper seal.

NOTE: Before removing pressure gauge, place absorbent rags around line connection which is to be disconnected and remove fuse 28 from fuse holder again.

- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Test sequence (Vehicles with engine code BDC)

- Disconnect coupling of fuel supply line -1- (black or black markings) and catch escaping fuel using a rag.

NOTE: For this, press together buttons at hose connection.

- Connect pressure gauge (V.A.G 1318) using adapters ((V.A.G 1318/9 and 1318/17) to supply line and to hose to 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 -4- from fuel pressure regulator -3-. Fuel pressure should rise to approx.. 3.0 bar positive pressure rise.

NOTE: If fuel should escape at the vacuum connection of the pressure regulator, replace fuel pressure regulator, item 14.

- 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 (V.A.G 1318) 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).

If pressure does drop again:
- Check pressure gauge for proper seal.
- Check whether line connections, O-rings in fuel distributor, and fuel injectors are properly sealed.

If no leaks are found:
- Replace fuel pressure regulator, item 14.

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

- Erase DTC memory of Engine Control Module (ECM) to bring adaptation values into a neutral state, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes