Originally Posted by
Jonathan
Could also be the seal on the fuel sender. If it isn't perfectly seated/sealed, it can come sloshing up around the edges when you're driving and then the air rushing by takes it from there into the cabin.
A good test to see if this is happening is to gain access to the top of the fuel tank by removing everything from your trunk, including the carpet board and spare tire, and then remove the access cover that's under the spare tire. You can now see the top of the tank and fuel sender. Check to see if there is any obvious fuel wet spots first. If not, and there may not be if it has evaporated, leave everything out of the trunk just like you have it and go for a little drive around the block. While going about 10 mph or so, slam the brakes on hard and come to a complete stop (make sure your neighbour isn't driving right behind you first!). Now pull over safely and have a look at the top of the tank and fuel sender and see if it is wet. If it is, you know where your leak is. Credit to Dave S. (of course) for sharing that little trick with me a year or so ago.