Fuel door leak

So, I thought I was finished with my 68 Barracuda but, out pops another problem. The car was sitting on level ground and when I went out to take it for a drive I smelled gas. I opened the fuel door and saw that gas has traveled up the pipe and ran out thru the fuel door. Is this a common problem? I understand that gas will expand on hot days but, I have had this car for three years and never once seen this even on a humid 98 degree day in the south. Plus, it was only 85 degrees. I am at a lost and I would appreciate some help.