Fuel Pressure Regulator and Residual Pressure, Checking - I

Fuel Pressure Regulator And Residual Pressure, Checking







Special tools, testers and auxiliary items required
- Pressure gauge V.A.G 1318
- Adapter V.A.G 1318/7
- Adapter V.A.G 1318/10
- Hose adapter V.A.G 1318/13

Function
The fuel pressure regulator controls the fuel pressure and is dependent on intake manifold pressure.

Conditions
- Delivery quantity of Fuel Pump (FP) OK; checking. Fuel Pump, Checking - I

Work sequence







- Remove fuse 28 for Fuel Pump (FP) from fuse holder.

CAUTION: Fuel supply lines are under pressure. Wear eye protection and protective gloves to avoid injuries and skin contact with fuel. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.







- Disconnect fuel supply hose -1- from fuel rail -2- (counterhold on hex of fuel rail).
- Connect pressure gauge V.A.G 1318 with adapter V.A.G 1318/7/10/13.
- Open shut-off valve of pressure gauge. Lever points in direction of flow - arrow -.
- Install fuse 28 (fuel pump) into fuse holder.
- Start engine and run at idle speed.
- Measure fuel pressure.
- Specification: about 3.5 bar positive pressure







- Pull vacuum hose off of fuel pressure regulator - arrow -.
- Fuel pressure must rise to approx. 4.0 bar positive pressure.

NOTE: If fuel drips from the vacuum connection of the fuel pressure regulator, replace fuel pressure regulator.

- Switch off ignition.
- Check for leaks and residual pressure. Observe pressure drop on pressure gauge. After 10 minutes there must be a residual pressure of at least 2.0 bar.

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







- Wait until pressure has risen, and then switch off ignition. At same time close pressure gauge V.A.G 1318 shut-off valve (lever perpendicular to flow direction - arrow -).
- Watch pressure drop on gauge.

If the pressure does not drop:
- Test check valve of fuel pump.

If the pressure drops again:







- Open shut-off valve on pressure gauge V.A.G 1318 (lever in flow direction - arrow -).
- Start engine and run at idle speed.
- Wait until pressure has risen, and then switch off ignition. At same time pinch return hose -3- tightly together.

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

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

Assembly is performed in the reverse order of removal. Also observe the following:
- Before removing pressure gauge, remove fuse No. 28 and put cleaning rags back around line connection which is to be disconnected.
- Fasten fuel supply hose to fuel rail