Fuel Pressure Regulator and Residual Pressure, Checking

Fuel Pressure Regulator And Residual Pressure, Checking

Observe safety precautions.
Observe rules for cleanliness.

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, check. Fuel Pump (FP), checking. Testing and Inspection

Vehicles with engine code AEG, AVH, AZG

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
- V.A.G 1318/10 adapter
- V.A.G 1318/11 adapter
- VA.G1318/16 hose adapter
- VAS5024 assembly tool for spring-type clamps

Work sequence
- Remove cover in front of fuse holder.

- Remove fuse no. 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.

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

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 to adapter (V.A.G1318/10) at supply hose and to adapter (V.A.G1318/11) and hose adapter (V.A.G1318/16) at supply line.
- Open pressure gauge shut-off valve. Lever points in 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.

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

- Switch ignition off.
- 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 pressure gauge shut-off valve (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. Testing and Inspection

If pressure drops again:
- Open pressure gauge stop valve (lever in 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, 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). Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

Vehicles with engine code BDC

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
- V.A.G 1318/9 adapter
- V.A.G 1318/17 adapter

Work sequence
- Remove cover in front of fuse holder.

- Disconnect coupling of fuel supply line -1- (black with white marking) and catch escaping fuel with a rag.

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

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.G 1318) using adapters (V.A.G 1318/9 and 1318/17) to supply line and to hose to fuel distributor.
- Open pressure gauge shut-off valve. The lever points in 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.

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

- Switch ignition off.
- 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 (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 Fuel Pump (FP) check-valve. Fuel Pump (FP), checking. Testing and Inspection

If pressure drops again:
- Open stop valve of pressure gauge (lever in 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 together tightly.

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

Vehicles with engine code BEV, BCD

NOTE:
- The fuel pressure regulator regulates the fuel pressure to approx. 4 bar.
- Fuel pressure regulator is located on fuel filter.

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

Work sequence
- Remove cover in front of fuse holder.

- Disconnect coupling of fuel supply line -1- (black with white marking) and catch escaping fuel with a rag.

NOTE: For this, slide securing ring -2- into connection -1-.

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.G 1318 using adapters V.A.G 1318/9 and 1318/17 to supply line and to hose to fuel distributor.
- Open pressure gauge shut-off valve. Lever points in direction of flow.
- Re-insert fuse 28 (fuel pump) in fuse holder.
- Bleed fuel system.
- Start engine and let run at idle.
- Measure fuel pressure.

Specified value: approx. 4.0 bar positive pressure

- Switch ignition off.

If specified value is not obtained:
- Replace fuel pressure regulator.
- Bleed fuel system.
- 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 specified value is obtained:
- Check for proper seal and residual pressure. Observe pressure drop on pressure gauge for this. After 10 minutes at least 3.0 bar positive pressure should still be present.

If residual pressure falls below 3 bar positive pressure:
- Start engine and let run at idle.

- Wait until pressure has built up, and then switch off ignition. Simultaneously close V.A.G 1318 pressure gauge shut-off valve (lever perpendicular to direction of flow (arrow)).
- Observe pressure drop (engine side) on pressure gauge.

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, place cleaning rags again around line connection which is to be disconnected and remove fuse 28 from fuse holder again.

If pressure does not drop:
- Check line connections to fuel tank for proper seal.
- Test check-valve of Fuel Pump (FP). Fuel Pump (FP), checking. Testing and Inspection

If no malfunction is detected in fuel lines and Fuel Pump (FP) check-valve is OK:
- Replace fuel pressure regulator.
- Bleed fuel system.
- 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