The fuel gauge in my 2000 7.3 has been giving some funny readings. Sometimes I fill up the tank and the gauge only says 3/4. Other times it's been stuck near empty even when there's plenty of fuel. Now I've pulled the tank and, well, I don't see anything wrong. The float arm moves freely. The ohm readings are consistent as I move it up and down. The floats do in fact float in a cup of water. I plug the sender back in and move the arm, and the gauge gives sensible readings. Anything else I should check?

 

As far as reading 3/4 when you fill it up at the pumps, check out harpoon mod. Essentially, the pumps shut off shuts off the fuel long before the tank is actually full. While you have the tank down, do the hutch mod too.

 

I had the same issue. Did the mods on the tank, checked the float and sending unit and it still would stick in spots.
I found it to be connected to my ignition switch. If I turned the switch on and the fuel gauge didn't read right I would switch it back off and then slowly back on and it would correct itself. I ended up changing the plastic actuator switch on the underside of the steering column and it helped but every now and then I have to still play with the switch.

Now I always set the trip odometer to zero when I fill up, just to be on the safe side.

 

I thought mine was going wacky to, well it is but it has a consistency. At about 5/8 of a tank the needle falls to below empty and when tank gets to about 3/8 full the needle comes back up. Sometimes it does just fine but it does this about 95% of the time. I would like it to work right but if this is all the worse it gets I can live with it vs the effort to drop the tank.

 

Sounds like your sending unit has a bad spot. Problem I found is the sending units for these trucks are outrageously priced.

 

IDI-Charlie did a good write up on repairing our sending units

https://www.ford-trucks.com/forums/1...r-success.html

 

Mine used to do that but it cleared up, hasn't done it in years. I'm not sure what fixed it, I did the in tank mods and cleaned everything up including the connections, plus I run Stanadyne and a lot of times B-20. I do know when I started running B-20 in our old Mercedes it cleaned the fuel system up gradually, maybe it did something for the truck too.....it just works fine now and I'm not questioning it. Another factor which may have something to do with it, I keep my tank mostly full all the time. When on a trip I always fill it up before parking for the night and when arriving home I fill it again before putting it away.