Quantum Syncro AWD L5-2226cc 2.22L SOHC (1987)
Fuel Pressure: Testing and Inspection
Differential Pressure Test
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 closed, activate the fuel pump and read the pressure.
Differential pressure should be 0.2 to 0.5 bar (3 - 7 psi) below system pressure.
5.
If the pressure is not within specification:
a. Disconnect the fuel distributor lower chamber return line from the fuel pressure regulator, and hold over a measuring container.
b. Plug the open connection on the fuel pressure regulator.
c. Activate the fuel pump, and measure the fuel quantity.
Fuel output should be 130 - 150 cc/min
d. If fuel quantity is OK, replace the differential pressure regulator.
e. If fuel quantity is not within specification, replace fuel distributor.
6.
Connect test harness (VW 1315A/1) to the differential pressure regulator.
7.
Disconnect plug from the coolant temperature sensor, and connect a 15K ohm resistor across the terminals (tool VW 1490).
a. With the ignition switched ON, and the fuel pump activated, differential pressure should be 0.7 - 1.2 bar (10 - 17.5 psi) below system
pressure.
b. Differential pressure regulator current should be 50 - 80 mA.
8.
If the pressure reading is not within specification, and the current is OK, replace the differential pressure regulator.
9.
If the pressure and current readings are both incorrect:
a. Remove test harness from differential pressure regulator.
b. Check resistance of differential pressure regulator.
c. Resistance should be 17.5 - 21.5 ohms.
10.
If resistance is not within specification, replace differential pressure regulator.
11.
If resistance is OK:
a. Check ground wire of the coolant temperature sensor.
b. Check power supply fuse and wiring.
c. Check terminal connections on the CIS-E control unit, coolant temperature sensor, and differential pressure regulator, for corrosion, burning,
or loose connections.
12.
If the connections, wiring, power, ground, and resistance are all OK, replace the control unit.
