First thing to do is to determine if the pump is off or always running. If it never comes on, it could be just the 30 AMP fuse that sends the voltage to it, to verify this go to pump connector Pin C (12VDC). If the voltage is not there or you checked the fuse first for an open and it's bad, then you are good to go. If not, proceed-- check for 12VDC at PinB (ignition voltage) which is needed for the pressure switch. Verify that PinA on the pump connector shows continuity with chassis ground. Then check the resistance of Pins B to D on the pump, it's a coil so it should have some resistance. Then also while making resistance checks, go across pins A and C and verify an open circuit. If you get to these resistance checks and that are not as above, then the pump is bad. Another way to verify that Pins B to D on the pump is good is to check at Pin A of the pressure switch and if 12VDC is there, then you know that the ignition voltage is getting to the pressure switch.
Darrell Jackson
Stock '87 GN
