i have 93 f-150 with 5.0 my problem is i filled the front tank up and my rear tank half full i drove it for awile on the rear tank i returned from my destination and fuel was coming out of my front tank i tighten the cap and it stopped later i went to check on it and thier was fuel still at the top and just pours out when i take the cap off and my gauge reads over full on my front tank what might be my problem

 

you overfilled the tank and due to a pressure change the area that the fuel has taken up has incre3ased and the tank's not big enough to accomodate for it. did you fill up elsewhere? likee... on a mountain or somehting? differnt climate? Extreme Temperature change? As the characteristics of Gas change depending on the enviroment in which you are in. Will become more or less dense.

 

These older ford sometime do not have check valves, so when you run your back tank with a full front tank i will overflow. best suggestion is to get a check valve put on your fuel pump or to run off the front tank, then the back then the front to used what ever flowed into the front tank. I had this problem in my 1990 5.0 but fixed it when i put a new fuel pump in