Leaking Fuel from cap.

i dont know what it is but sometimes i will get fuel 'gas' coming from out the fuel cap, ive had this before where fuel was actually pouring out.
did same gas again today, cant tell if fuel is leaking from the bottom of car of if its exhaust heat i can see.
what is this? fuel tanks getting too hot and causing gasses etc?

help if you can.

i found this, some interest in the vapour lock thingy..

"Fuel injected Cabriolets/Rabbit Convertibles from 1984* to 1993 have 2 electric fuel pumps.  The main fuel pump is located beneath the car, passenger side, in front of the gas tank.  The second pump, called a transfer pump, is located inside the gas tank; access to this pump is on the passenger side under the rear seat.  Both of these pumps are wired to the fuse/relay panel.  If a pump fails to operate, check the fuse and relay first.

A fuel pump check valve is connected to the main fuel pump.  This device helps in preventing vapor lock and helps maintain fuel system pressure after the engine stops.  On CIS engines, this part can be replaced independent of the pump; on Digifant engines, the check valve is part of the fuel pump and cannot be replaced separately"

Taken from this site
http://dana.ucc.nau.edu/~kaw5/fuel.htm

Seems like a check valve could be a problem here! on my 1.6 Carb model the check valve must be connected to the fuel filler pipe. And there was one when i replaced mu filler neck.

Interesting reading!

There is no primary lift pump on a tintop Mk1, it was only used on later Cabbys then the Mk2.

Have you checked the fuel cap seal (there is one fitted to the screw in type cap, not sure about the bayonet one)?

Cheers
Rajan

nop mines bayonet.
i will check 2moro but dont think its that, i can smell petrol all the time near my car, in traffic i can see it coming out (not petrol, just fumes) of the key hole in the cap.