why does front fuel tank leak gas?

also i see a crack on the back of the nozzle that also makes the gas leak which looks like an easy fix but isnt all of my problem

Did you find the fix to this problem? My 1986 F150 has the same problem. I've owned the truck for many years, but I don't drive it much and keep it in the garage. It just has 150K miles. Problem first started when I noticed a vacuum release with the front tank when I removed the cap to fill, now tank pressure is so much that gas blows by the new cap. I want to know how to fix this dangerous problem.

I have 1978 ford f150 that has a hole near the top and to the right of the fuel sending unit if you're looking from the front of the vehicle. The hole presses against a pad on the frame or the pad was on the tank and has now stuck to the frame. It appear that when I reinstall the tank it will seal off. Does anyone have any knowledge about this design and can verify that my idea is accurate?

Have same issue. You have a fuel selector valve mounted under the cab that switches between tanks... it also sends unused fuel BACK to the gas tank from the engine. When the selector valve goes back, it sends gas to the OPPOSITE tank...and usually will not let the truck run on the other tank either... you flip the switch and the truck will die. REPLACE the valve... got mine for $176 on eBay. Rust and pressure will force gas to leak from one tank (mine was front too). Have to replace the tank next. In my case, the fuel pump in the rear tank (which was working fine) is now bad. Considering the pump in the front tank was disgusting, I'm sure the rear one is too. The parts are 32 years old...they don't last forever. New pump, new sending unit, new tank. Good for another 300,000 miles!

Pardon my misspelling... "When the fuel selector valve goes BAD....it sends gas to the wrong tank..." is what I meant.

i have the same issue but from bottom