Fuel gauge trouble

[fomocoguy]

I just need some advice from some of you fellas who have been through problems with your factory fuel gauge. Here's my problem. My fuel gauge shows 3/4 tank when full, and when it's empty I fill it and it only takes 10 gallons. I figured I had some kind of funky small tank, but then I read that 19 g was the smallest in cab tank, so I'm pretty sure my gauge never reads full and shows empty when it's really at about half a tank. So it's working, but not correctly, and not sporadically. It's always wrong in the same way. So, any ideas? Thanks!

[ToughOldFord]

More than likely the tank sending unit. Full the wire at the tank, ground it, then put the ignition switch to the 'on' position. If gauge then reads 'full' then you have a bad sending unit.

[fomocoguy]

Ok thanks! I'll try that today or tomorrow and see what happens.

[Thunderfoot]

I have the same problem with mine, just haven't gotten to it yet.... I figured mine was either the float rod was bent or the float was sinking (is not floating to the top) as it reads empty way before it gets to the bottom of the tank plus when full only reads 3/4... I did check my gauge by shorting the sender wire as TOF said and my gauge went to full so I'm good there.
Let me know what you find out if you pull your sending unit before I get to mine.

[fomocoguy]

Well I just tried the grounding trick and it went to full, so it definetly has something to do with the sending unit. I think tomorrow I'll pull it out and mess with it. I'll pull the float and drop it in some water and see how it does. I'll let you know!

Does anybody know of any sending unit rehab tricks, or do you just have to replace them?

[Lar4t9r]

If you have not already looked at the fuel gauge tech on this site, here's the link:
http://www.fordification.com/fuel-sending-units.htm

Might help.

[fordman]

i think i would try adjusting the ipvr first before i went messing with trying to replace the sending unit or guage.

[Thunderfoot]

i think i would try adjusting the ipvr first before i went messing with trying to replace the sending unit or guage.

If you ground the sending unit wire and the gauge goes to full (which he did) the ipvr and gauge is ok.