95 Pathfinder Fuel Fumes - rear end

My 95 Pathfinder has a rather severe fuel smell in the right rear end right after the engine is shut off. After the engine has been off for about 5 minutes the smell is gone. I cannot find a fuel leak and suspect it is gas fumes leaking out of somewhere back there since the fuel tank/fuel cap has no pressure in it immediately after engine shutoff. I have check all the fuel lines, the canister, the check valve, the fuel pump access port and everything looks good and checks fine based on the shop manual. I have also replaced the fuel cap. The problem is worse in the summer. The fuel smell is not there when the engine is running and you cannot smell it inside the vehicle. It does not seem to matter how much fuel is in the tank.

I am fairly sure it is fuel vapor so what all should I be looking at back there and how do you tell where you have a vapor leak?

Could the fuel fill neck have a rust pinhole? Any other ideas? I have been chasing the problem for a year or so and am running out of ideas.

Jim