Hey everybody, been a long time since I've posted but I'm having a big problem. My front tank leaks when it's filled over half way, so I only use the rear tank. Recently my front tank started to leak again, and now after driving the truck I notice fuel leaking past the gas cap, and if I take the cap off gas will shoot out of the filler!! Also, may be a coincidence but, my gas mileage is very bad, like 50 miles on one tank of gas. I'm wondering if these problems are related to each other???
This is on my 86 5.0efi dual tanks

 

your fuel selector valve is shot. crawl under the drives side and follow the fuel lines til you see a round black container about the size of a fist. there should be 4 fuel lines going to the rear and 2 to the front. when those things fail they can do all kinds of crazy stuff like diverting fuel from one tank to the other. they are VERY prone to fail and unfortunately pretty expensive to replace.

 

I had a feeling it could be that. Looks like I'll be hitting the junkyard for another one to replace this one, I was hoping it would be something simple like that, it's been so cold here I don't need any long projects, no heated garage at my house!