Had this problem. tightened nut, then Rebuilt once, then replaced twice - still leaked
https://www.fordbarn.com/forum/showt...ight=gas+valve
Barn recommended replacing with Brattons part #13160 - issue solved. Made in the USA, 3 year warranty. Most others are made overseas.
Another possibility is to find an original - try rebuilding it.
https://www.brattons.com/fuel-shut-o...-gas-tank.html