I just bought a Ford F-100 1978 truck and the fuel gauge isn't working, anyone have any ideas on how to fix it?

 

More than likely it's either your sending unit, voltage regulator on the back of the instrument panel, fuel gauge, or and electrical fault (bad ground or something). You should probably do some troubleshooting or just take it to a shop...

 

"More than likely......" I think you nailed everything it could be.

 

Alright, thanks guys.

 

Well what was mentioned is everything it could be. You gotta start somewhere and narrow it down. Does it ever work? Does it read full or empty all of the time or somewhere else? Does it just sweep periodically back and forth? Do the other gauges work?

It's the biggest PITA but I'd start with checking the sender first since every time I have a fuel gauge problem that is where I end up eventually after trying everything else.

 

All the other gauges work, and it stays on empty all the time.

 

I'm new to these trucks so someone else may know better but my vote is for the sender or sender wiring/ground.

 

this also just happened to me last night. As the story goes: I've had my truck 2-3 days on the road now, last night with 3/8's of a tank I went to the gas station and threw in $40. It read 7/8's about. On my short commute back home it dropped and sat right at E. now this morning it doesn't even move up to E.....wha happened? Trouble is I'm still getting used to the gas mileage and judging it, needles to say I'm a lil nervous now. How does one go about fixing the possible solution mentioned earlier?

 

To check the fuel gauge - ground out the (orange wire?) connection from the gauge - if it reads "full," the gauge is functioning properly.
This link explains it better than I can.

Fuel Tank Sending Unit Tech - FORDification.com

 

Dirtgood- check the connection in dash and make sure its tight. My connections were loose and the needle would sit at E. Pulled the panel and the nut on back of gauge was loose. Tightened it up and it jumped up to full

 

My float had a hole in it,which made it read "E" all the time.

 

Sweet, sounds like a good lead ya filthy beast lol.

Sc79 it could very well be the dash. I had it semi apart the other day replacing bulbs. I couldn't get that main electrical connection to the back of the cluster loose so I gave up trying until I was sure about how to go about it. I may have loosened something in the process. The fuel gauge did work after putting it back together though....for a day or two. The bottom right gauge (believe engine temp) hasn't worked at all in the two or so weeks I've owned it, maybe I can kill two birds with one rip apart/put together (best case scenario). I'll try that tonight and let yas know how it works out.

 

Wasn't able to get to it today but soon

 

Agree on all the diagnostics. if all the other gauges work, the dash voltage regulator is probably OK. On mine (78 F250) the gauge wire can be disconnected just in front of the firewall for diagnostic test. My gauge didn't work and the sender was OK. I didn't really want to pull the cluster and send it out for repair (and wait) so an Autometer fuel gauge from Summit mounted to the left of the steering column fixed it.

 

I find that about 2 out of 3 times its the float getting old and taking on fuel and sinking. I buy new ones 5 at a time from bronco graveyard for about 8 bucks each. Thats about the only place I've found new ones for sale