gas gauge doesn't work...

One day I got in the Jeep :v6: and the gas gauge didn't move. I went to the gas station and realized it was still pretty full. Now I go to the gas station every couple of days to make sure I don't run out. All of my other gauges work fine, at least to my knowledge.
I know that I saw a thread in here about this exact problem, but for the life of me I can't find it. I seem to remember it having something to do with the wiring and the dimmer switch, but thats as far as I go. If this is the problem, could that also affect the brightness of my headlights? They're pretty dim, even after replacing them. I've just assumed it was the fact that it's almost 40 years old (I'm not saying that everything almost 40 is dim...no offense ).
Thanks!
Pete

 

Usually a ground wire has lost its contactiveness Dim Headlights and / or tail lights is a dead give away. Or if your turn signals makes the opposite lamp noticeably dim. Gas gages are notorious for bad grounds after years or decades.

 

Been down this road. If my old memory serves me correct the CJ sending unit is backwards. If you loose contact it reads full all the time. Mine quit last year I took it out of the tank and the float had a hole in it a little solder and it was good as new. Mike

 

Just be sure to drain the float real well and let it all dry out before you solder it, especially if you're using an open flame.

 

No open flame for me, and it had set for a week or so.

 

I just read a thread about rewiring and am wondering I should just go for it and re-do everything. I'm not sure what my Grandpa did to it or what the PO did either, but it's a mess under the dash.

 

Most JEEPs of this era are like that. They have things added and removed and most just leave the wire behind. When I got mine it looked bad up under the dash. I spent a day removing unused wire and low and behold most of the factory harness was still in great shape. Mike

 

The original sending unit ground itself to the tank by contact. The replacement aftermarket units come with a ground wire.

 

Your ground (negative) strap runs to your block if it is set up the factory way.
Could be you need to run a ground strap from the block to the body, at the firewall. This may also take care of the dim headlights. :hurrican:

 

So two years later and I am returning to this problem. The gas gauge reads empty. I fiddled with some of the wires under the dash and the gauge started working. A couple of days later, it went to full and didn't move. More fiddling with the wires and it went to empty and stayed. I figured it was a loose wire so I tightened everything up and tried again. Now the fuel gauge still shows empty and the temp gauge doesn't move off of cold.:? Any thoughts? I'm stuck...

 

I can't help you ,if it's the under seat tank, I just carry a stick . always reliable !!!!!

 

X2! FTW!

 

x3
i even marked mine ....

 

me too, jeep will run on flat ground with only 3/4".
---- thats funny I figured it was just me with the hillbilly gauge .quess ,I m not so different after all.

 

I thought if you take a wire off the sending unit and ground it and the gauge reads full then the gauge is good and the sending unit is bad. Have you tried this?

 

1975 version FSM: "A voltage regulator maintains a constant voltage to the gauges in normal operation. On early vehicles, this voltage regulator was mounted on the rear of the instrument cluster. On current vehicles, the voltage regulator is integr with the fuel gauge. Should trouble develop in the gauges, first check the regulator (fuel gauge on current production vehicle). If the voltage to the regulator is below 10 volts system low gauge readings will result. Voltage in excess of 16 volts will not affect gauge readings but may result in premature wear of the regulator contacts. If the voltage regulator is within the above limits, check the electrical connections to the regulator (or fuel gauge), especially the ground connection. If the readings of all the gauges is too high, or they all read too low, replace the regulator (or fuel gauge).
If the temperature gauge or heat indicator in the instrument cluster have failed, the cause may originate from the jumper bar shorting out against the instrument case. On later production vehicles, the jumper bar is covered with an insulating sleeve to protect it from shorting out against the instrument case. If the jumper bar does not have this sleeve, either install one or wrap the bar with plastic tape to half an inch from each end."

From your description, my guess is either the regulator or the jumper bar, probably the latter. You probably do not have an extra fuel sender unit that you can hook up to the gauge lead to actually check the cluster gauge (sender MUST be grounded), but you can get a good idea if it is working by checking its resistance under full tank and part tank with a multimeter (bat to one meter lead, tank wire to other). There should be a notable difference and it there is not, it is the sender unit. Hope this helps.

 

Here is a thread on 'gas gauge troubleshooting' .
note the link to jeepfan.com within the thread.
http://www.earlycj5.com/forums/showthread.php?t=34502&highlight=gas+gauge+troubleshooting

If you troubleshoot the problem you will be able to sort it quickly. If gauges regulator or sending unit are needed they are available new at reasonable prices.

Tom

 

Don't forget that the fuel gauge itself has a ground point at the rear of the gauge which grounds to the mounting speedo case. The speedo housing must have a good ground to the dash panel and the panel to tub and tub to frame. I have the battery negative cable going to both engine and frame.

 

Mine worked when I bought it and stopped working sometime thereafter. I took my sending unit out of the underseat tank and found that the float had developed a hole in it, thus always reading empty. I mickey moused a repair with a cork float from a snowmobile and it is working!

 

Thanks for the help. I hope to get out today and check it out. (I kinda like the stick idea though...)
I do have the jumper bar between the gauges, with a sleeve over it. I'll check it's condition.
Hope everyone had a great Christmas!