I haven't seen a post about this in a while so i thought i'd bring it to topic.
Since getting my ef last year i've ran into a few others who have experienced having the smell of gas inside their car. I've taken it to be of the common problems that occur when owning a crx (such as the tearing of the driver side seat or broken climate controls). Usually if i fill my gas tank only about 1/2 way, theres no smelly smelly. But now im determined to fix the problem! I've checked my lines and im positive there are no leaks, so im sure the smell is originating from the rear. Is there anyone out there who has had this problemo and fixed it?

 

check ur gas filler lid area the sealent that holds the insid part might be seperating from the body

 

I've had that issue before from two different sources. One was the hose that connects the filler neck to the tank (which I doubt is your problem). Also I had a leak at the gasket on the fuel sending unit.

Now when I had the leak on the sending unit it was as you described, you smell it when you fill it more than half full or if the car is going down a hill etc. because that gasket sits at the top of the tank.