T W A U ... The Chase...from...
Film, Media & TV0 min ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.Generally all petrol pipes are external to prevent this sort of thing. BUT the filler pipe has a breather pipe that should go back to the tank. If that is damage, or the overflow bit is, and the wheel arch seam is damaged it could let in fumes.
The other likely cause, again depending on car, is that there are sometimes a cut out in the boot floor which mates directly onto the fuel tank. From here you can get access to the fuel tank level sender/fuel pick up etc. I've seen on a few occasions that the sender/pickup unit hasn't been located properly allowing fumes to leak into the boot.
Another course is the boot not shutting properly and over rich exhaust gases, especially when choke is on, is being drawn back into the boot.
So, what vehicle is it? Japanese by any chance (or one with a Japanese engine?)
Depends on the car I guess. I have an ageing Renault 5 which began to smell of petrol particularly after filling up the tank. There was a split in the flexible plastic pipe which ran from filler to the tank, letting petrol leak when it was brim-full. Have a good look underneath (pu one set of wheels on the kerb to get some room to wriggle under, you'll usually see where the problem is.