I've done lots of searching but I can't seem to find an issue quite like mine.

When I use the rear tank, the fuel gauge works just fine. But when I switch to the front tank, the gauge stays where it was and doesn't move.

For example, I switched to the front tank when the rear was 1/4 full. The gauge didn't move. Switched back to the rear tank, drove until it was completely empty and stalled. Switched to front tank and drove. Gauge stayed at empty. Filled the front tank, and for whatever reason the gauge decided to work for a while and jumped to full like it should, but then it stuck at full. Just for kicks, I switched to the rear tank and stalled the engine, let the gauge sink to half tank and then switched back to front and restarted the truck. Gauge stayed at half.

Never seen anything quite like this. It's like the gauge isn't "updating" to show what's up with the front tank. What could be going on?

 

Did you check your connections? It sounds like a wiring issue to me. Start with the connections at the sending unit on the front tank.

 

I'll give them a look. Anything I should know about testing a sending unit?

 

It would be a bad selector switch or an open wire between the front tanks sending unit.

 

Mine does this too. Like a dummy I added 8 gallons to the front tank before even checking for sure it worked. I just went off what the guy I bought it from told me. He said it worked. I turned on the key and the guage read empty so I looking for all the gas on the ground lol. Luckily the tank, pump and switch works, just not the guage. Also until you get it fixed run some gas through it, don't just let it sit forever or your pump will probably quit working. I'm sure you know though though

 

Only on a Ford.

How much is a new sending unit?

I have a multimeter, can I test it with that?

 

Sorry I'm really not too sure if you could test w/ that or not. The part is about $50. Check on parts geek. Odd thing w/ my computer but I can't copy and paste or it crashes but I found it for my truck. Not sure what year your truck is but Motorcraft part 5304-05157575 is the part for a 92-93. I bet if you YouTubed it you could figure out how to do it yourself. From what I've heard that'll fix it

 

Weird thing here, yesterday I was out driving the truck around, looked down and the fuel guage was working. I at first thing I must have switched to the rear tank but nope, front one was working. It was pretty much where I thought the gas would be too so I'm not sure why mine quit then back on now. Probably a loose wire or something

 

Or a dead spot on the tank sending unit. Every F-150 I've ever had has a screwy gas gauge.

 

This sounds quite plausible for my situation. In my case I would bet the dead spot is everywhere but full tank.

 

First, it's inside the tank attached to your pump assembly.........basically a mechanical float with a two wire elec circuit to measure resistance (float position).............that elec hookup on the top of your tank may be dirty too--------------nonetheless, you're looking at dropping the tank (or lifting the bed) to get at things............30 minutes to lower tank/disconnect fuel filler and lines.........

 

I might cut right through the bed and make a little hinged door thing.

 

Just lower the tank. Chances are good that once you replace the float and pump, you'll never have problems with it again, ever.

 

That's exactly what I want to do...somehow without throwing sparks, maybe an air sheetmetal nibbler?
Mine has a plastic bedliner so not too concerned with mud or dirt getting to the tops of the tanks from the bed if I cut holes.
With all the bad press about FDM's, I'd like to be able to look at stuff in the middle of nowhere, in the dark, in the rain...you know what I mean.

 

Well it seems now the whole thing is borked. Both tanks are full but the needle stays stuck at 3/4 full no matter which tank I select. What the crap.