Residual Pressure

Fig. 1 Fuel Pump Relay Bypass:

1. Connect the pressure gauge with the proper adapter (VW 1318/5), and new sealing washers, between fuel line at the cold start valve, and lower chamber test connection on the fuel distributor.
2. Remove fuel pump relay, and install a jumper wire with in-line switch, Fig. 1.
3. Disconnect the plug from the differential pressure regulator.
4. With the gauge valve open, activate the fuel pump for 30 seconds, then turn off.
5. Minimum pressures are:
2.6 bar (38 psi) -- after 10 minutes
2.4 bar (35 psi) -- after 20 minutes
6. If system does not hold adequate pressure:
a. Check fuel pump check valve
b. Check all fuel line connections for leaks
c. Check cold start valve
d. Check sensor plate clearance (if sensor plate does not reach its full rest position, fuel could be leaking through the injectors)
7. If everything tests OK, replace fuel pressure regulator, and repeat residual pressure test.
8. If system still leaks, replace fuel distributor 'O' rings.