I recently purchased an original instrument cluster off of ebay for my 86 bronco, I bought it because it had a tach on it and my bronco does not and i wanted one, I also figured it might fix the problem with my fuel gauge. Well i switched the speedometers and installed the "new" gauges with their original wiring and platic they came with. I found my fuel gauge was fixed and everything worked great.
The next morning i drove to the gas station and filled it up, about 3/4 full the fuel gauge made a funny sound and started acting like the old gauge did, when its full it shows it only has about 1/4 of a tank. I got this bronco for my grandpa and he has since passed away, he was always someone who if it didn't fit he would make it. I was wondering if he might have replaced the sending unit with one that is for a 16 gallon tank and since mine is a 32 gallon maybe that is the reason for the gauges not working properly, well i know it was a lot of words for such a little problem but any help would be appreciated, thanx

 

This is not an uncommon problem; I had the same problem with my '86. Assuming that you've got an EFI motor, the fuel sending unit is integrated with the fuel pump. The sending unit will eventually fail (I think it either cracked or rusted), and if you want the guage to work properly, you'll end up replacing the fuel pump.

 

well thank you for your help but it is carborated and the fuel pump is seperated from the sending unit do you think it might just be the sending unit

 

well thank you for your help but it is carborated and the fuel pump is seperated from the sending unit do you think it might just be the sending unit

 

I just had this same exact problem on my 1990 Ford Bronco. I dropped the tank and pulled out the entire sending unit. When you do this you will see a YELLOW float. It looks like a minature steel garbage can. Over time these become rusty, and get holes in them. That is what happened to mine. This caused it to fill up with gas, and not be able to float, in turn causing the gas gauge not to work. I got a new float for free from a local junk yard. They only cost $10 form a ford dealership. That is what fixed MY problem.

 

thanks for your help bronco351 I'll give that a try and see what happens