Jeff,
Open sender lead = pegged gauge
Grounded sender lead = zero gauge reading
Clear??? Disregard any other 'hints' that suggest otherwise from posts!!!
OK ... you have half of the system working! The 'needle jump' is indicative of an open to the sender! Try grounding the connector at the sender location with the ignitionswitch on ... if the needle does not go to zero ... you still hve an open somewhere. Try a temporary ground at the gauge input lead just to make sure it is working correctly. Two likely sources are that 1/4" female Faston connector at the sender (broken strands inside wire at crimp) or a bad connection at the 14-pin connector to the front of the car on the relay/fuse/CDI panel in engine compartment. Clean the 14-pin connectors with isopropyl alcohol and an old toothbrush on the male side and pipe cleaners in the receptacles of the female side. The connectors are silver-plated ... so be careful not to scratch or abrade away the plating!
Test the wire to the sender again after cleaning the 14-pin connectors. If still no 'zero' indication, wiggle the wire just 'aft' of the connector ...while firmly holding the Faston to ground. If intermittent or still open, cut off the connector and strip the Green/Red wire about 3/16" and test the gauge again by grounding the bare wire. If you now have a zero indication, install a new female connector.
If still open go back to the 14-pin connector from the main wiring harness to the front of the car and find the Green/Red wire at Pin 4 ... test with test clip to ground ... zero indication obtained, now?
Let us know how the testing proceeds??? Good luck!
