What is the best way to test the filler tube for leaks? I don't know if its the relief that's giving off the fuel smell or if I have a crack in the filler tube.

 

If the gas smell is towards the rear of the car, it's probably the tube. The excess pressure relief is taken care of up front, by the charcoal canister and purge valve located just behind the passenger headlight.

I suppose you could have a bad purge valve, thus not purging the tank pressure, and maybe fumes are escaping from around a bad gas cap - anything is possible.

You can remove the gas door, and the filler neck plastic inside, and maybe shine a flashlight in there and look at the filler neck, without removing the tank - that may yield some insight.

 

When I got home from Garner, I could smell it more underneath the car than from the cap area. The relief valve underneath the car, what happens if it gets clogged?