OK guys, Filled her up today drove maybe 10 miles. Got home went back out about 6 hours later fired her up started driving and looked at my fuel gauge and it read below empty. Still driving I went through all possibilities knowing it can't be a fuse I was hoping maybe I got siphoned i stopped at the station it took 1 gallon and it's full. So where's the problem and where do I start to trace it down and fix it? Any help would be greatly appreciated !! Thanks
You will need a helper to sit in the car to watch the gauge while you do this. Have the helper sit in the drivers seat with ignition key on. To eliminate sending unit problems, pop the wire off the gas tank unit and ground it to the body. If gauge and wiring is all good the fuel needle will head towards the full mark. If that works the problem is the sending unit. If that doesn't work, you will need to trace down a wiring failure or power problem. There is also a small voltage regulator on the back of the cluster that provides low voltage to the fuel gauge. It is rare that they fail, but they do sometimes. One spot in the wiring that is a problem on these cars is the 2 pin connector in the trunk. Look for it by the drivers side trunk well around where the wire comes through the rubber grommet from the gas tank. Wiggle that one around and have the helper watch the gauge and see if that fixes it. I have had a couple cars where that corroded and the connection failed.
Follow what Eric said, that is a great write up. I have found that 80% of the time it is the fuel sending unit and then the regulator after that. One time though it was a bad contact on my instrument cluster and had to replace the board.
The float was missing from my sending unit. When I took it out and tried to clean it up, the wires fell off. I resoldered them and re-used my old unit with a new float.
The proper procedure is use a 10 ohm resistor from wire on tank sending unit to ground. With resistor, gauge needle should just reach full mark, indicating it's in calibration(grounding lead buries pointer). Using jumper leads with alligator clips no help is necessary. If that gives no reading, refer to other issues mentioned. I recently ran above check on my Cobra Jet, as it never reads more than 2/3 even when full. It passed. Need to pull sending unit, maybe one of these days.
Good point about the ohms resistance. I guess I should have been a little clearer about shorting the wire to ground. If you do it - do not let the fuel needle go all the way. The helper is there to tell you to stop when it is rising up towards the full mark.
Thanks for all the input and sorry I took so long to update. So next day gauge worked, it is hit or miss with the gauge sometimes it works sometimes it doesn't. it always reads 3/4 when filled up. Same time fuel gauge started I lost my heater blower motor. Coincidence or possible connection ?
My heater blower motor has a ground to the engine side of the firewall. I would re work that ground and see if your heater motors starts again. Find out if/where the fuel gauge is grounded and fiddle with that too.
Most old cars that I have owned with inaccurate or non functional fuel gauges have been the sender in the tank. That being said, I just replaced mine and now the fuel gauge only works if you tap on the dash. I even reached up in there while my girlfriend watched the gauge.. I works both when I lightly tap the gauge nuts and the resistor. It is being very tricky to pinpoint. If there were all sorts of good clusters laying around to choose from I would buy one, but..
