I have a 94 Toyota 4X4 pick-up with a V-6. There is a strong gas odor in the cab of the truck sometimes when I stop. Once the truck starts moving, the odor somewhat dissipates. This does not occur all of the time but is becoming more frequent. The shop states they cannot diagnose the problem unless the truck is currently exhibiting the problem. I was told I would be charged either way.

I was thinking it could be the charcoal canister clogged under the hood. I pulled the gas tank vent tube and shot air through it so it is not clogged. Anyone have any ideas?