Volkswagen Workshop Service and Repair Manuals

Notes:

• ◆ Fuel pressure regulator regulates the fuel pressure to approx. 4 bar.
• ◆ Fuel pressure regulator is located at the fuel filter (in the fuel tank).

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

• ◆ V.A.G 1318 Pressure gauge
• ◆ 1318/9 Adapter
• ◆ 1318/17 Adapter
• ◆ 1318/23 Adapter
• ◆ V.A.G 1348/3 A Remote control

Test sequence

• ‒ Remove cover in front of fuse holder.
• ‒ → Remove fuse 28 (fuel pump) from fuse holder.

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

Note:

To do this slide safety ring -2- into the union -1-.

• ‒ → Connect the pressure gauge V.A.G 1318, as shown, with the adapters 1318/9 and 1318/17.
• ‒ Open shut-off tap on pressure gauge. The handle points in direction of flow.
• ‒ Refit fuse 28 (fuel pump) in fuse holder.
• ‒ Start engine and run at idling speed.
• ‒ Measure fuel pressure.
      Specification: Approx. 4,0 bar

If the specification is not obtained:

• ‒ Switch off ignition.
• ‒ Check whether the fuel pump can build up and maintain the pressure , Check non-return valve for fuel pump.
• ‒ Check fuel pressure regulator => Page 24-38.

If the specification is obtained:

• ‒ Switch off ignition.

• ‒ Now check for leaks and holding pressure (compound system). Watch 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 the pressure has built-up. At the same time close pressure gauge V.A.G 1318 cut-off tap (handle cross through-flow direction -arrow-).
• ‒ Observe pressure drop (engine side) on gauge.

If the pressure drops again:

• ‒ Check pipe connections, O-rings on fuel manifold and injectors for leaks.
• ‒ Check pressure gauge for leaks.

Note:

Before removing pressure gauge place a cloth around the connections to be loosened.

If the pressure does not drop:

• ‒ Check non-return valve of fuel pump, check fuel pump non-return valve.
• ‒ Check fuel pressure regulator => Page 24-38.

Check fuel pressure regulator

Test prerequisites

• ● Non-return valve for fuel pump OK.,
  Checking => page 20-42.
• ● Fuel supply line OK..

Test sequence

• ‒ Remove cover in front of fuse holder.
• ‒ → Remove fuse 28 (fuel pump) from fuse holder.

• ‒ → Connect remote control V.A.G 1348/3A with adapter cable V.A.G 1348/3-2 to contact 28a to fuel pump and battery positive (+).

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

Note:

To do this slide safety ring -2- into the union -1-.

• ‒ → Connect pressure gauge V.A.G 1318 with adapter V.A.G 1318/23 and V.A.G 1318/17 to the fuel supply pipe.
• ‒ Close pressure gauge shut-off tap (lever diagonally to direction of flow -position -B-).
• ‒ Operate the remote control V.A.G 1348/3A
      for approx. 10 seconds
  to build up a system pressure of approx 4 bar.
• ‒ Observe pressure drop on gauge. Over a duration of 30 minutes the pressure must not drop below
      3,2 bar.

If the pressure drops further:

• ‒ Check line connections for leaks.

If no wiring fault is detected:

• ‒ Renew fuel pressure regulator.