Fuel tanks
 

I have a 1986 F150 with a front and rear tank. The rear tank has been leaking for quite some time so I have been using only the front tank. I took both tanks off and decided to replace only the front tank. The sending unit on the back tank was badly rusted, so I just took all the connections to the back tank, tied them off, wrapped them in plastic and duct taped it to keep them clean in case I want to put a rear tank on the truck in the future. After replacing the front tank, the gas gauge quit working. Do they both need to be hooked up, or is there a problem with the connection on the front tank?

Thanks!!