The other day, someone posted (I think in Electrical) about a bladder in the fuel tank. I'm wondering, along these lines, about my problem (no, not my mental problem, I know about that one).
My fuel tank occasionally reads 1/8th tank. Rarely when it's full, and more often when I have less than 1/2 tank. Any suggestions?

Thanks !

Chances are good the sensor in the tank is shorting. But you could have a wire to the sensor partly shorted as well.

The gauge has power and ground in the dash. Then a sensor wire goes out of the dash to the tank sending unit. The tank unit is a variable resistor. The resistor position is controlled by the float in the tank. When there is no resistance, such as an empty tank or shorted wire, the gauge reads empty. If the wire comes off or is cut, or the tank resistor open circuits, the gauge goes about 1/4 tank past full. The fact that your gauge reads lower than it should means you have a partial short or bad sending unit, or the gauge itself failed.
Next time it's reading too low, unhook the wire to the tank and see if the gauge goes past full. If it does the problem is in the tank. If not the problem is likely in the gauge. (This could be a partly shorted wire but that' fairly rare unless corrosion is a factor.) I know that's easier said than done. Reaching the connection on the tank is not likely to happen without dropping the tank. Getting into the dash is not an easy choice either. You may want to get into the wiring harness going through the car and disconnect it there. There is at least one connector between the dash and the rear of the car. (Sorry, I don't remember where it is. If memory serves it's a 16 gauge pink wire.)
It is possible to lose the ground from the tank, but that would be an open circuit and the gauge would read past full.
If the sender in the tank is sticking and the float is not going up in a full tank, that would make it read low as well. This would probably not be an intermittant problem. It would raise to a given point and stay there until fuel level dropped enough for it to start working right again. The bladder could make it stick, so could a worn out sending unit or bad float.

Ken Styer

Does your fuel gauge read full when it is full normally? I guess what I am asking is does your fuel gauge work properly most of the time and occasionally reads 1/8th when it actually has more gas? You may have a problem with the float in the tank. When the sending unit normally goes, the guage will go past full and stay there all the time. Same thing will happen if the sending unit is not grounded properly.

Ken's the "Man". I would take his advise over mine. Good Luck!

wow, thanks for the explintation !!!

I've been into the console, things looked good there. Guess it's probably in the tank (never reads past full). So, either the sender, float, or possibly bladder.

Dang thing is, local dealership a while back, told me that was like $400 for the sender/float. Any suggestions if I do need this ass'y? Any chances it will be in a condition where I can repair it?

Thanks Alot !!

Sometimes they are repairable, sometimes not. You don't know until you get there. Check it before you pull it. If you do take it out, let me know what you find and we'll go from there.

Ken Styer

Last year I went through the whole project of replacing the tank sending unit and when that didn't fix it I replaced the fuel gauge. Finally came to the bladder in the tank. Dropped the tank and it seemed good but you can't tell when the tank is empty. Bent the float on sending unit so it would work. Not as accurate but better than nothing. Good luck, you might have to drop the tank to get the sending unit out if the bladder is in the way.