Hunting down the elusive fuel stink

The pursuit of the dreaded fuel smell in an old BMW 2002 has been the bane of many an enthusiast and owner. For the past year I have been chasing down the vaporous demons. One drive would be a sweet smelling back road carving session, the next a brain cell obliterating fuel huffing romp. From what I could tell, only heavy acceleration and tight, fast turns instigated the scent.

My first coarse of action was to replace all of the under-hood rubber seals. That did nothing. I replaced the fuel line. Nothin’. I then noticed that my 40/40 weber carb had developed a leak which resulted in a puddle of gasoline collecting on the hot intake manifold. That puddle quickly evaporated and rushed into the passenger cabin, searching for I.Q. points to destroy. A new 38/38 carb helped a bit, but I was still getting heavy fumes when I’d take quick turns on a full tank. The fuel tank itself was then suspect. But after removing it and pressurizing with compressed air, I found no obvious leaks.

So what I finally determined was that the fuel vapor catch, #5 on this diagram, needed to be reconnected. I had been running the fuel vapor exhaust line out of the trunk the way European 2002s had been fitted. Additionally, in order to make up for my lack of ecological consideration, I decided to incorporated an activated charcoal canister as well…home made, of course.

Activated charcoal is available from a number of online sellers, but I ran down to my local pet shop and grabbed a big bottle (1.8L) of aquarium filter carbon for about $19.


Next I fashioned a 1 liter screw top bottle into a charcoal canister by epoxying two barb fittings in and filling the bottle with charcoal.

I ran the vent tube from the rubber filler neck to the plastic expansion tank then into my custom made charcoal canister. From there the exhaust tube runs under the trunk. To secure the canister I affixed a piece of Velcro tape to the bottle and stuck it to the carpet on my trunk floor.

After two test drives I’ve not been able to recreate the fuel stink. And while I had the tank out I decided to scrub it down and give it a few coats of paint. I also replaced the rotted open cell foam that lines the lip of the tank support with fresh closed cell and RTV sealant.


(Close up of closed cell foam)


(You can also see the fuel vapor exhaust tube rerouting and charcoal canister in this shot)