Volkswagen Workshop Service and Repair Manuals

Checking fuel pressure regulator and holding pressure

Special tools and workshop equipment required

t	K-Jetronic pressure tester -V.A.G 1318-

t	Adapter -V.A.G 1318/9-

t	Adapter set -V.A.G 1318/17-

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

–  Remove fuse No. 28 (fuel pump) from fuse holder.   Note For reasons of safety, the voltage supply to the fuel pump is interrupted through the removal of fuse SB 28. Otherwise opening the driver door would start the fuel pump.   WARNING Fuel system is under pressure! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

–  Disconnect fuel supply line coupling -1- (black or black marking) and collect fuel which escapes with a cloth.   Note Press in securing ring to release fuel lines.

–  Connect K-Jetronic pressure tester -V.A.G 1318- to fuel supply line and on hose to fuel rail using adapter -V.A.G 1318/9- and adapter set -V.A.G 1318/17-. –  Open shut-off tap of K-Jetronic pressure tester -V.A.G 1318-. 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. 2.5 bar.

–  Pull vacuum hose -1- off fuel pressure regulator -2-. The fuel pressure must increase to approx. 3.0 bar. If the specification is not attained: –  Check fuel pump delivery rate → Chapter. If specification is attained: –  Switch off ignition. –  Now check for leaks and holding pressure. Do this 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 the pressure has built up. At the same time, close shut-off tap of K-Jetronic pressure tester -V.A.G 1318- (handle at right angles to direction of flow -arrow-). –  Watch pressure drop on pressure gauge. If the pressure does not drop: –  Check fuel pump non-return valve → Chapter. If the pressure drops again: –  Check K-Jetronic pressure tester -V.A.G 1318- for leaks. –  Check line connections, O-rings on fuel rail and injectors for leaks. If no leaks can be found: –  Renew fuel pressure regulator.   Note t  Before removing the K-Jetronic pressure tester -V.A.G 1318-, place a cloth around the connection to be loosened and remove fuse 28 (fuel pump) from fuse holder. t  If the fuel pressure regulator is renewed, erase learnt values and adapt engine control unit again → Chapter.