i have an '86 f150, bought used, fuel gauge never worked. recently pulled the fuel tank and found broken ground wire. fixed that and got guage reading when operating the sender by hand. reinstalled it in the tank, fueled up, and you guessed if, no fuel gauge reading. have double checked ground repair, it is good.

any suggestions?

 

it may be a bad fuel gauge if it moves when you do it by hand not in th tank i had to replace one myself for my 93

 

I've also seen where when the get installed the float gets caught on something and doesn't work properly.