volkswagen Workshop Repair Guides

Volkswagen Workshop Service and Repair Manuals

Checking intake air system for leaks (unmetered air) > < Checking injectors
Motronic fuel injection and ignition system ä 07.95
Motronic injection and ignition system
Checking fuel pressure regulator and holding pressure

The fuel pressure regulator controls the fuel pressure dependent upon intake manifold pressure.

Special tools, testers and auxiliary items

  • ◆ Pressure tester V.A.G 1318
  • ◆ Adapter 1318/10
  • ◆ Adapter 1318/11
  • ◆ Adapter 1318/16

Test conditions

  • ● Fuel pump delivery rate OK, checking:

=> Repair group 20, removing and installing parts of the fuel system, checking fuel pump

Test sequence

 
N24-0085
Warning!
The fuel system is pressurized! Before loosening hose connections or opening the test connection, wrap a cloth around the connection. Then release pressure by carefully pulling off the hose/sealing cap.

  • ‒ → Pull fuel supply pipe -1- off fuel manifold -2- and connect using adapter 1318/10 to pressure tester V.A.G 1318.
  • ‒ Connect pressure tester V.A.G 1318 to fuel manifold -2- using adapter 1318/11 and 1318/16. Open pressure tester shut-off tap (handle in throughflow direction -arrow-).
  • ‒ Start engine and run at idling speed.
  • ‒ Check fuel pressure.
         Specification: Approx. 2.5 bar
 
V24-1060
  • ‒ → Pull vacuum hose - 1- off connection -2-. The fuel pressure must rise to
         approx. 3.0 bar.
  • ‒ Switch off ignition
  • ‒ Check for leaks and holding pressure by watching pressure drop on gauge. After 10 minutes there must be
         a residual pressure of
    at least 2 bar.

If the holding pressure drops below 2 bar:

 
N24-0084
  • ‒ Start engine and run at idling speed.
  • ‒ → After the pressure has built up switch off ignition and at the same time close pressure tester V.A.G 1318 shut-off tap (handle 90°to throughflow direction -arrow-).
  • ‒ Watch pressure drop on gauge.

If the pressure drops again:

  • ‒ Check fuel pump non-return valve.

=> Repair group 20, removing and installing parts of the fuel supply system, checking fuel pump

If the pressure does not drop:

 
N24-0085
  • ‒ → Open pressure tester V.A.G 1318 shut-off tap (handle in throughflow direction -arrow-).
  • ‒ Start engine and run at idling speed.
  • ‒ After the pressure has built up switch off ignition and at the same time clamp-off the return pipe -with blue arrow- on fuel manifold.

If the pressure does not drop:

  • ‒ Renew fuel pressure regulator.

If the pressure drops again:

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

Checking intake air system for leaks (unmetered air) > < Checking injectors