SO my adventure began a few weeks ago. Started with carb being rebuilt, to finding water in gas, to new tank and lines and fuel pump. I was changing the sending unit, but since the place I ordered from sent the wrong on, I decided to use the old one since it worked fine. Now, the tank I had was stock {16 gal} the new one is 17 gal.
Here is the fun....ALL week in the heat cussing because it wasn't getting gas. I have a 5 gal gas can, I put it all in...the gauge read 1/4 full which I thought was a bit off.....still wouldn't run, if I took the line AND the sending unit and drop it in a gas can...it fired up, just not when in the tank......
Finally I say "hey" go get more gas.....so I added 5 more gallons....{technically 4.2 gal} so tank has a total of about 7ish gallons.
Guess what...IT RUNS!!!! And test drove it....
I guess my sending unit it a tad bit too short to suck up the 1st 3 gallons.....which leads me to a question.....

**** Why would the gauge read MORE if the sending unit is too short?? with the 7ish gallons now, it reads 3/4 of a tank.......I don't get it

 

Sounds almost like the pickup on the sender is rusted out and sucking air, even a pinhole will ruin your day. as far as the sender reading funny, could be just plain old ford bad sender syndrome.

 

I had a similar problem with my sending unit. If you have the time to fiddle with the SU you can take it apart and on the inside there are metal windings that you can wind closer or farther apart to control what the gauge reads. It is however very time consuming, but it saved me the 80 bucks for a new one. Plus, as others ave mentioned, make sure you have no pinholes or a leaky float.

 

****Update on the update...feel even MORE stupid!!!!!*********
SO, I decided to take the sending unit out, measure it and measure the depth of the new tank and old tank........It's official, in all my anger and frustration I overlooked 1 little thing.....the sending unit was sitting in 90deg backwards!!

The little **** on the unit only line up one way on the new tank, the issue was the tabs were cut backwards. The pickup on the sending unit it at an angel because where the lock ring goes in tilted a bit. So being 90 deg. backward...the pickup arm was sticking out almost angeled 60 deg UP away from the gas...the float was sideways more/less and in the 1/2 position so when it hit the gas, shot up to full......the resolve.....cut the **** off the sending unit and locked it back in place.....now I have a 1/4 tank which should be right...and the stem is pointing straight down like it should be...
My dad always said, never work on ANYTHING when your mad and frustrated because you'll overlook SOMETHING...in my 30 sum odd yrs I FINALLY understand.....

 

*grin*

-ct

 

Thats pretty messed up.

Glad you finally figured it out.