Carbon canister - fuel smells...

Drew20

Drew20

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On our 70s classics the fuel tank has a breather line which vents directly to the atmosphere, just underneath the rear bumper. This is to ensure that the tank can vent (and so not over pressure) on a hot day, and to stop the pump pulling a vacuum when the engine is running, and drawing fuel from the tank.
On my 1981 6er there were three vents lines running from the tank neck to a carbon canister, and the carbon canister vented to the atmosphere. Routing the vent via a load of activated carbon draws the vapour out, so your garage smells better.
I was thinking of doing a mod to my E9, by placing a carbon canister (probs from a VW) behind the wheel arch, and routing the tank vent through this.
I'm not sure why the E24 set-up has three lines between the tanks and the canister, overkill?
Also, modern cars actively purge the canister by connecting it to the car's intake via the purge valve. My E24 didn't have this, so I was planning to ignore that detail.

Any thoughts?
 
My 72 e3 has vent line from fuel fill neck to canister under battery tray and then line to intake.
 
cool, thanks for that. I was not aware that E3s had this gear. Is it much bother to deal with? On my E24 this was no bother, and it just sat there in the boot/trunk. Do you have a piccie you could share?
Putting E3 parts in the boot would be preferable to random VW parts, however I'm still not planning to connect it up to the intake
 
Original E3 location is under the battery tray. If you are doing this because you smell gas, you should not with venting under the rear bumper. Perhaps a crack in the vent line before it exits the trunk?
 
bavbob said:
Original E3 location is under the battery tray. If you are doing this because you smell gas, you should not with venting under the rear bumper. Perhaps a crack in the vent line before it exits the trunk?
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Well I can check the line again, I did remove the line to check it out last year. My garage smells of fuel, especially near the rear of the car, worse on a hot day. Vapours are getting out down this line, hence the plan to put a carbon canister in the line.
Thanks for all of the info re the E3 set up. I've been looking at other BMs also. Other than the purge system it's all the same. Routing from the tank to a plastic expansion tank, then to a metal carbon canister (I think)
 
I suspect you have a leak elsewhere, possibly from your sender unit oring, filler neck hose, fuel hose, gas cap, or the tank itself. Bypassing the plastic hoses and expansion tanks removed my smell, i live in a very hot climate and i have no smell from my setup.
 
Thanks Steve, most parts are new there: new hoses, clamps and sender unit seals last year, plus a recent tank by the previous owner. But the hard line running to the hole by the bumper looks original (although I replaced the short rubber section) and I don't know about the tank cap. What I might try to do is pressure test all of this, by putting a compressor on the vent line to very gently put pressure on the tank, seals etc. plus the vent line itself. Hoping any leaks would be obvious by smell
 
I pressure tested the tank and associated pipes at 2psi, as much as I dared as the tank clearly bowed upwards even at this modest pressure
Anyway, the tank seals, tank filler cap, vent line, etc held at just over 2psi for two hours, until I got bored and had mercy on the poor inflated tank! I refitted everything as it was, but also fitted a grommet where the vent pipe exits the boot space by the bumper. I assume it's meant to be there, and had gone missing in a previous resto.
Will post back once I've done something with a carbon canister
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Drew20 said:
I pressure tested the tank and associated pipes at 2psi, as much as I dared as the tank clearly bowed upwards even at this modest pressure
Anyway, the tank seals, tank filler cap, vent line, etc held at just over 2psi for two hours, until I got bored and had mercy on the poor inflated tank! I refitted everything as it was, but also fitted a grommet where the vent pipe exits the boot space by the bumper. I assume it's meant to be there, and had gone missing in a previous resto.
Will post back once I've done something with a carbon canisterView attachment 90490View attachment 90491
Click to expand...
I picked up a parts car today. May have a usable carbon canister if you’re interested.
 
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