Checking Fuel Pressure Regulator and Holding Pressure

Checking Fuel Pressure Regulator And Holding Pressure

Engine codes AVH, AZG
The fuel pressure regulator regulates the fuel pressure depending on intake manifold pressure.

- Pressure tester V.A.G1318
- Adapter V.A.G 1318/10
- Adapter V.A.G1318/11
- Hose adapter VA.G 1318/16
- Hose clamp pliers VA.G 1921

Work sequence

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

CAUTION: Fuel system is under pressure. Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

- Pull off supply line -1 - and collect leaking fuel with a cloth.

- Connect pressure gauge V.A.G1318 to fuel supply line and to fuel rail with adapters V.A.G 1318/10, V.A.G 1318/11 and hose adapter V.A.G 1318/16.
- Open shut-off tap on pressure gauge. Lever points in direction of flow - arrow -.
- Refit fuse 28 (fuel pump) in fuse holder.
- Start engine and run at idling speed.
- Measure fuel pressure.
- Specification: approx. 2.5 bar

- Pull vacuum hose -1 - off fuel pressure regulator - 2 -.
- Fuel pressure must increase to approx. 3.0 bar

If the specification is not obtained:
- Check quantity supplied by fuel pump.

If the specification is obtained:
- Switch off ignition.
- Check for leaks and holding pressure by observing pressure drop on gauge.
- After 10 minutes, there must be a residual pressure of at least 2.0 bar.

If the holding pressure drops below 2 bar:
- Start engine and run at idling speed.

- Open shut-off tap on pressure tester V.A.G1318 (handle points in direction of flow - arrow -).
- Start engine and run at idling speed.
- Switch ignition off after pressure has build-up. At same time pinch/seal return hose together.

If the pressure does not drop:
- Replace fuel pressure regulator.

If the pressure drops again:
- Check line connections, O-rings on fuel rail and injectors for leaks.
- Check pressure gauge for leaks.

NOTE: Before removing the pressure tester, remove fuse 28 again and place a cloth around the connections to be loosened.

Engine codes BEV, BGD
The fuel pressure regulator regulates the fuel pressure to approx. 4 bar.

The fuel pressure regulator is located on the fuel filter.

Special tools, testers and auxiliary items required
- Pressure tester V.A.G 1318
- Adapter V.A.G 1318/9
- Adapter V.A.G 1318/17
- Adapter V.A.G 1318/23
- Remote control V.A.G 1348/3A with adapter cable V.A.G 1348/3-2

Work sequence

- Pull off fuel supply line on connection -1 - and collect leaking fuel with a cloth.

NOTE: To do this slide securing ring -2-in connection -1 -.

- Connect pressure gauge V.A.G1318 to fuel supply line and to fuel rail with adapters V.A.G 1318/9 and V.A.G 1318/17.
- Open shut-off tap on pressure gauge. Lever points in through-flow direction (position - A -).
- Refit fuse 28 (fuel pump) in fuse holder.
- Start engine and run at idling speed.
- Measure fuel pressure.
- Specification: approx. 4 bar

If the specification is not obtained:
- Switch off ignition.
- Check that fuel pump can create and maintain this pressure, Checking fuel pump non-return valve.
- Check fuel pressure regulator.

If the specification is obtained:
- Switch off ignition.
- Check for leaks and holding pressure (entire system) by observing pressure drop on gauge.
- After 10 minutes, there must be a residual pressure of at least 2.0 bar.

If the holding pressure drops below 2 bar:
- Start engine and run at idling speed.

- Switch ignition off after pressure has built up. At same time close pressure tester V.A.G1318 shut-off tap (handle at right angles to through-flow direction - arrow -).
- Observe pressure drop on pressure gauge (engine side).

If the pressure drops again:
- Check line connections, O-rings on fuel rail and injectors for leaks.
- Check pressure gauge for leaks.

NOTE: Before removing pressure tester place a cloth around the connections to be loosened again.

If the pressure does not drop:
- Check fuel pump non-return valve.
- Check fuel pressure regulator.

Checking fuel pressure regulator

Requirements
- Fuel pump non-return valve OK, checking
- Fuel supply line OK

Work sequence

- Pull fuse No. 28 out of fuse holder.
- Connect remote control V.A.G1348/3A with adapter cable V.A.G1348/3-2 to contact 28a to fuel pump and battery positive (+)

- Pull supply hose -1 - off fuel filter outlet.

NOTE: Press locking ring inward to release fuel lines.

- Connect pressure gauge V.A.G1318 to fuel filter outlet with adapters V.A.G 1318/23 and V.A.G 1318/17.
- Close pressure gauge shut-off tap (lever at right angles to through flow direction - position - B -).
- Operate remote control V.A.G1348/3A for approx. 10 seconds to fill fuel filter and to build up a system pressure of approx. 4 bar.
- Observe pressure drop on gauge.
- After 30 minutes, pressure must not drop below 3.2 bar.

If the pressure drops further:
- Check line connections for leaks.

If no fault in lines is detected:
- Replace fuel pressure regulator.