Mystery Fuel Leak

[typ53]

So the Quattro (1990 RR) has a fuel leak somewhere in or near the fuel tank. 

It's noticeable as a fuel smell in the cabin after it's been on boost for a bit and after the car is shut down it seeps from somewhere under the fuel filler flap. 

I don't know if it's a leaky fuel cap seal or a perished seal or perhaps the fuel tank is getting pressurised. 

Does this sound familiar to anyone? 

Any ideas on where to look to try and track down the cause?

[John Stone]

Not sure about leaks around the fuel tank, however there have been documented cases of leaking fuel lines, get underneath and check them, have a good look around the fuel filter too.

John

[GlenT]

May sound silly, but make sure the fuel cap is on properly.
Had the same symtoms on mine years ago. Fuel smell in the car, small amount of fuel leaking out from the over flow drain from the filler when it sloshed out from cornering.
Turned out that the last time I filled up with petrol the forecourt attendant (one of the very few times I let them do it) didn't put the cap on properly.

[typ53]

Thanks guys, will try those suggestions and report back.

[typ53]

Tightening the fuel cap helped somewhat, it's still seeping out a bit but not nearly as much.  I'll try and track down a suitable seal for the cap and go from there.

[colingrant]

Yeah the caps leak. If I park on an angle with a full tank it dribbles a bit. Likewise on hard cornering with a full tank.

[blue 0v]

My black QC leaks were the the fuel filler pipe goes in to the tank, around the welds.so if you fill over half tank it smells.found the leak when I was at station filling and having a nosey around the tank.jay