Fuel Smell '68 Tank Setup

[EngineerDoug]

Hello,

I have a stock '68 fuel tank that is giving off fuel vapors when parked. This only happens after I refill the tank. I have a mechanical fuel pump with a return style regulator after the carbs get fed. This return line goes back to the tank. The other vent line on the fuel sender assembly is connected to a stock hard line that runs up through the trunk floor and then back down into the frame rail. Factory style setup. The fuel cap itself is non-vented, and lives behind the license plate ('68 coronet).

I am interested in ideas to use some sort of charcoal canister with the fuel vent to reduce this issue. At present there is no vacuum valve/line/circuitry from the engine; I would rather not add this complication unless it's really necessary.

Would this solution be as simple as connecting a charcoal canister/filter in series with the tank vent line? I would appreciate anything that others have tried with success; thanks.

 

[Kern Dog]

This is how these cars were when they were new and roaming the country. They still smelled better than cars with road draft tubes.
Old cars smelled of gasoline. That is how they were. Are you a young guy that grew up with all new cars having EFI and computers?
In the 70s, there were attempts made to route the gas tank to a charcoal cannister mounted up front near the core support. Everyone that I knew ripped that stuff out of their cars.

 

[Dennis H]

With exception it is a characteristic as above. Condition is worsened if parked “nose down.

 

[EngineerDoug]

I found the problem, and a way to reduce the stink. Turns out that when the tank is full, and it's a warm day, pressure in the tank builds because the tank vent tube inside the tank is submerged in fuel. So pressure is forcing fuel out through the vent tube and into the frame rail. When I open the cap there is a noticeable pressure release - you can hear it. For now I will loosen the cap once the car is parked inside the garage to stop this from happening.

And no, I'm not a young one...65 this year. I remember my dad used to love the smell of gasoline.

The garage is attached to the house and the wife noticed the fuel smell migrating into the house. Our bedroom is above the garage to boot.

Something about wife's sense of smell - and it becomes even more acute once you have kids. I swear she can smell colors.

 

[Kern Dog]

Good thing you got it figured out.
I can’t help it. I love the smell of gasoline. One time I had some 110 octane leaded gas left over. I ran it in my lawnmower.
It smelled like 1968 again. I loved it.

 

[R/T Boy 67]

I don't know if this would make a difference, but the vapour return line from the fuel pump is the one that connects to the sending unit, not the tank vent.

 

[dadsbee]

Nothing better than the smell off napalm 100LL in the morning...

 

[eldubb440]

Bel Ray 2 stroke oil emanating from a European dirt bike exhaust is pretty darn good

 

[68gtxman]

My 1967 Barracuda had a big gas smell (which I love by the way). I removed the tank and found that it had a crack on its top, that I never would have found if I didn’t remove it. It’s great that you found your issue so quickly!

 

[EngineerDoug]

I did some searching and found a vented/locking cap that fits perfectly. So far the issue seems greatly reduced. I am sure some vapors will still escape, but we'll see once I take a cruise in this warm weather.

Prior to this there was enough pressure building in the tank to force gas all the way up the vent tube - gas was dripping on the garage floor under the right side rear frame rail.

In case anybody is interested, the cap is a Gates P/N 31670.

 

[Some Car Guy]

I think the problem is worse these days then say 25 years ago. The vapor pressure of today’s gas is really high. Race gas is much more stable and seems to help, but wow that costs a lot for a street car