why can i smell petrol when i drive my 72 vw beetle?

Here is an answer for you and some links with pictures.

If you smell fuel inside the cabin or inside the trunk, you've got a leak somewhere. Either you haven't used brand new fuel lines or you've got a component that no longer holds its integrity. Sometimes, the expansion tube and charcoal canister (which are no longer offered) don't work and must be accounted for. If that's your problem, you must reroute some lines to block of these two things. Avoid any leaks at all costs. In reality, a 1971 Super doesn't have to pass smog tests, and because of that, it doesn't have to be environmentally sound.

Now try this link...I know that answer confused me too :-) It even tells you which hoses to disconnect and how to by pass things if need be.

http://www.vwtrendsweb.com/tech/0307vwt_1971_beetl...

This takes you to part 1..look on the left side of the screen and click the tech button...then look for part 16...that will have all the pictures.

Have fun...I know I'm going to. I just haven't gotten to step 16 yet :-)

you can only be smelling petrol from one place, the front. If you were smelling it from the back, you should be able to get down on your hands and knees and see petrol dripping on the ground. I suspect it is the hose connection from the gas cap entrance to the tank someplace. Since you smelled it right after you filled up, fill up again someplace close to home and go through some of these motions these other people suggest. Read all the questions and see if any of them have the solutions.

check in the engine compartment.(I am doing this from memory so I may be a wee off) The grey hose that goes to the fuel pump from the fuel tank. Put your thumb and forefinger around it and slide it down its length. check your fingers for wetness. Do the same from the fuel pump to the carburetor(I am assuming it is carbed) Again check for wetness. The Wetness is petrol. Inspect the ends of those grey hoses, are they cracked, splitting or other.. Flex the hoses. Oh, it is OK to have the engine running while you do this, in fact if might help in finding the leaker. Now flex the grey hose. It is rubber wrapped in fibre so it flexes to a 1" circle fairly easily. If wetness now shows on the hose, replace the hose.

The rubber can't last half as long as the steel.

Lift the liner off the floor of the trunk. Under neath is the tank. See all the tubing? Even the small stuff? check all of the rubber or cloth covered bit for wetness. Sounds to me like either a vent line(small ones) or filler neck (bigger ones) has dry rotted and leaks with a full tank. Wouldn't hurt to check the engine compartment either.

Very common problem the hose between the tank andthe gas filler it gets old and breaks down over time just replace it

I had a 76 and it developed a leak in the gas tank (petrol tank). They were notorious for that. Cheap steel used in the tanks and no lining.

you have a leak between the filler cap to the tank. check the hose and clamps in between.

....have a sniff around to see if you can pinpoint it..look around the tank area...