Fuel gauge pegs at full when tank is empty then crashes to empty after a minute
78CJDave
Jeeper
- Posts
- 1
- Thanks
- 0
- Location
- Charleston, WV
- Vehicle(s)
- 1978 CJ5
258 4.2L
Dana 300 Transfer
Dana 30 Front
AMC 20 Rear
First off just want to say thanks to everyone who has posted about fuel gauge problems. I've learned quite a bit, but unfortunately, I'm still having issues.
I've got a 1978 CJ5 . Just replaced my old steel tank with a new plastic 15 gallon. New sending unit, and a number of new fuel gauges lol. Everytime I install a fuel gauge, I get a reading of FULL. Even when there is only half a tank of fuel. After it reads full for a couple minutes, the gauge burns out and crashes to empty (the last gauge I put in actually came back to life after driving around for a bit and read accurately as to how much fuel was in the tank???). I've checked resistance in the sending unit (19 ohms which matches up with the known fuel level of a little over half a tank), ground from the sending unit to the frame is continuous and is a good known ground, continuity is good between the gauge and the sending unit, and the gauge cluster is grounded to the dash. I even bought a new aftermarket gas gauge and it is still pegged at full when the tank is only a little bit over half full. What in tarnations is going on?? Haha, getting the fuel gauge to work has been my most important improvement when I started fixing things up and it's all I have left to do and just can't figure it out. I've printed off Strenks article and have gotten very familiar with it. Someone said something to me this morning about possibly the voltage regulator in my alternator could be bad. And that this might be sending too much juice to the gauge. Any suggestions would be greatly appreciated.
Also, just for fun (with the ignition off), I tested resistance between the red wire that supplies power to the gauge and ground. I got a reading of zero resistance. Is this correct?
I've got a 1978 CJ5 . Just replaced my old steel tank with a new plastic 15 gallon. New sending unit, and a number of new fuel gauges lol. Everytime I install a fuel gauge, I get a reading of FULL. Even when there is only half a tank of fuel. After it reads full for a couple minutes, the gauge burns out and crashes to empty (the last gauge I put in actually came back to life after driving around for a bit and read accurately as to how much fuel was in the tank???). I've checked resistance in the sending unit (19 ohms which matches up with the known fuel level of a little over half a tank), ground from the sending unit to the frame is continuous and is a good known ground, continuity is good between the gauge and the sending unit, and the gauge cluster is grounded to the dash. I even bought a new aftermarket gas gauge and it is still pegged at full when the tank is only a little bit over half full. What in tarnations is going on?? Haha, getting the fuel gauge to work has been my most important improvement when I started fixing things up and it's all I have left to do and just can't figure it out. I've printed off Strenks article and have gotten very familiar with it. Someone said something to me this morning about possibly the voltage regulator in my alternator could be bad. And that this might be sending too much juice to the gauge. Any suggestions would be greatly appreciated.
Also, just for fun (with the ignition off), I tested resistance between the red wire that supplies power to the gauge and ground. I got a reading of zero resistance. Is this correct?
