I’ve been the proud owner of my first truck, a 1977 6.6L F150, with DUAL TANKS!
This truck spent many years just sitting and I picked it up with an 1/8 tank of gas. I was so excited to have two tanks that I topped them both off at the pump and since then the gauge has read empty. Have been through a few tank cycles since, and even ran both tanks out but still not a blip of gas showing on the dash. What do you think?
I would check to see if the gauge is getting power. If that is ok then check to see if power is getting to the sensors. If you have power there then the sensors need to be checked. If there is a switch involved for the tank sensors then check that also.
Back in the day the float was brass.
In our shop three months ago we removed the sender of a 75 to find the 1 1/4" dia brass was corroded to less than 1/8" left on the bottom.
You may very well have a float… that doesn’t .