Volkswagen Workshop Service and Repair Manuals

The fuel pressure regulator regulates the fuel pressure depending on intake manifold pressure.

Special tools, workshop equipment, test and measuring appliances and aux. items required

• ◆ V.A.G 1318 Pressure gauge
• ◆ 1318/9 Adapter
• ◆ V.A.G 1921 Pliers for spring-type hose clips

Test conditions

• ● Fuel pump delivery rate OK, checking:

=> Rep.-Gr. 20; Removing and installing parts of fuel system; checking fuel pump

Test sequence

• ‒ → Disconnect the fuel supply pipe coupling -1- (black or black marking) and catch the fuel which escapes with a cloth.

• ‒ → Connect pressure gauge V.A.G 1318 to fuel supply pipe/hose and to hose to fuel rail using adapters 1318/9 and 1318/17.
• ‒ Open shut-off tap on pressure gauge. The handle points in direction of flow.

• ‒ Start the engine and run at idling speed.

• ‒ Measure fuel pressure.
       Specification: Approx. 2.5 bar
• ‒ → Pull the vacuum hose off fuel pressure regulator -arrow- . The fuel pressure must increase to
       approx. 3.0 bar.

If the specification is not obtained:

• ‒ Check quantity supplied by fuel pump.

=> Rep. Gr.-20; Removing and installing parts of fuel system; checking 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 the engine and run at idling speed.

When the fuel pump has built-up the pressure again:

• ‒ → Switch ignition off after the pressure has built-up. At the same time close pressure measured device cut-off tap (handle cross through-flow direction -arrow-).
• ‒ Watch pressure drop on gauge.

If the pressure does not drop:

• ‒ Check fuel pump non-return valve:

=> Rep.-Gr. 20; Removing and installing parts of fuel system; checking fuel pump

If the pressure drops again:

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

If no leaks can be found:

• ‒ Renew fuel pressure regulator , item 1 .

When the pressure gauge is removed after completing the test:

• ‒ Switch off ignition.
• ‒ Hold a cloth over the adapter to be loosened and remove pressure gauge.