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).

Recommended special tools and equipment
- V.A.G 1318 pressure gauge
- Adapter 1318/9
- V.A.G 1318/17 adapter

Test requirements
- Parking brake must be engaged or else day time driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Delivery quantity and check-valve of Fuel Pump (FP) OK, check => page 20-19. Fuel Pump (FP), checking.
- Ignition switched off.

Test sequence
Observe safety precautions.
Observe rules for cleanliness.
- Remove cover in front of fuse holder.







- Remove fuse no. 28 (fuel pump) from fuse holder.







- Disconnect supply line -3- (black with white marking) and catch escaping fuel using a rag.

NOTE: Press in securing ring to disengage the fuel lines.

WARNING:
- The fuel or fuel lines in fuel system can become very hot (danger of scalding).
- In addition, the fuel system is under pressure. before opening the system, place rags around the connection area and release pressure by carefully loosening the connection.
- Wear protective goggles and protective gloves when working on the fuel system.







- Connect pressure gauge (V.A.G1318 using adapters V.A.G1318/9 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 (arrow).
- Re-insert fuse 28 (fuel pump) into 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 pressurize.
- Switch ignition off.

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

- 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 built up, 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, Checking - I

If pressure drops again:







- Open shut-off valve of pressure gauge. The lever points in the direction of flow (arrow).
- Start engine and let run at idle.
- Wait until pressure has built up, and then switch off ignition. Simultaneously pinch return hose tightly together.

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

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

NOTE: Before removing pressure gauge, remove fuse no. 28 again and put cleaning rags back around line connection which is to be disconnected.

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