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One possibility is any rubber fuel lines, even stainless braided lines. Modern gas will permeate right thru them. Holley and Napa have a rubber line that will not do this. Nylon is another good replacement but this is more involved.
I can confirm it's the carb. My 71 had the same problem and with an attached garage I was worried about fumes getting into the house, they were that strong. After I converted to EFI I have never smelled any fumes at all, even with a vented gas cap.
1970 with dual pump 750 CFM carb and sealed tank. Garage fills up with gas vapors when stored. Appears to be evaporation from carb. Any solutions?
could it be with a sealed tank that when the fuel expands due to heat it pushes through the pump into the carb and keeps supplying fuel to the carb to be leaked and evaporated? Have you looked into the manifold through the secondaries to see it fuel is puddling there?
From: At my Bar drinking and wrenching in Lafayette Colorado
You have a problem with the fuel system. Cars with carbs do not stink up the garage with gas fumes. I have a garage full of carbureted cars - both Q-Jets and Holley-type double pumpers, and there are no fuel fumes in my garage. When new, LT1 Camaros and Corvettes with Holley carbs sat on the Chevy dealer showroom floor inside buildings with fuel in the carbs and they did not stink up the showroom. Every car manufactured from 1900 up through the 1980's had carburetors, and they did not stink up every household's garage in America with gas fumes - it didn't happen. It still does not happen unless you have some type of problem with your fuel system. You're leaking or seeping fuel from somewhere.
I'm having the same problem.
The fuels now are more volatile, and combine that with the much lower boiling point of the alcohol in it, and it seems to percolate and evaporate away.
I haven't heard of any real solution except ventilation.
1970 with dual pump 750 CFM carb and sealed tank. Garage fills up with gas vapors when stored. Appears to be evaporation from carb. Any solutions?
Have you checked the cork gasket between the gas tank filler neck and the tank? Overfill the tank to almost top of neck, pull rubber boot from around neck and see if gasoline is seeping out where the gasket is located.
I have an old 3310 Holley and never have any smell.
Another thing to check is what has been done to the return line assuming it has one?
If the fumes are bad enough in your garage, it can create a dangerous situation. A spark from a light switch being turned on/off could result in igniting such fumes. IMHO, you need to fix it pronto.
My garage is sealed up tight with two 78’s both with Qjets. If I smell gas I know there’s a fuel leak somewhere. One time it was the fuel inlet needing a little more torque. Another time it was the rubber fuel line from pump to carb. That was lucky to not have started a fire, and happened with it’s planned metal replacement already on the shelf. Another was the vapor canister. I had replaced the activated carbon with aquarium charcoal without first getting it bone dry. It dried out on it’s own after a few weeks and stopped dripping on the floor. When I refreshed the next one I left the charcoal out in the sun for a bit first. Both cars are left with heaters under them for weeks at a time, locked in the garage with no gas smell.
Charlie
I’ve owned cars, motorcycles and boats with vented gas tanks and never had gas fumes in the garage.
Check every fuel line and connection from the fuel tank up to the carb.
You will probably find a hose or connection that is seeping fuel.
It may not be enough to drip yet but you’ll usually see some wetness around the connection.
My 73 smelled up the garage when I first brought it home.
I found the fuel line between the pump and carburetor was seeping fuel but not dripping.
I replaced the line and the smell was instantly gone and has been for the past 7 years.
Don’t forget to check the fuel return line if you have one.
Last edited by OldCarBum; Nov 6, 2022 at 03:45 PM.
I have a 78 in my garage with a remanufactured Qjet from Lars and have all of the emission stuff including the charcoal canister connected and a vented gas cap and the only smell is when I shut her down and my guess is that it's from the exhaust...
FWIW I have 2 refillable odor plug ins at opposite end of my garage and it smells like vanilla....
JJ78
Here is a picture of my gas tank when i removed it. The cork gasket between the filler neck had lots of cracks in it , so the fuel was spilling onto the tank as i was driving around. It also disintegrated the tank sticker i was hoping to find. I installed a new gasket of new fuel lines.
Another item, depending on your year, is the fuel separator valve attached to the tank.
Those are plastic and do crack allowing vapors to be emitted into the air.
They are easy to replace, but the problem is finding a good one and not a cheap China pos that will crack and fail almost immediately.
