Fuel vapor odor

[68 Toro]

On warm days, the lovely scent of fuel vapor is noticeable inside and around my 1968 Toronado. It's been like this since I bought it 11 years ago.

I had the gas tank removed and "refreshed" (see photos), and all the fuel lines from tank to carburetor replaced. This did not eliminate the smell.

Any suggestions?

[bcroe]

You did well to go through the tank and fuel lines. I am going to suggest going over
all the emissions control stuff, including the tank gas cap. Perhaps something isn't
venting or releasing pressure properly, and its pushing gas out somewhere. I forget
what is in a 68, but I had some problems in the 70s till such things were corrected.

Bruce Roe

[Otto Skorzeny]

I have noticed the same smell around all my vehicles (all of which are carbureted). I am fairly certain that it's a result of the ethanol fuel used today.

I believe what we're smelling is fuel evaporating from the carburetor. Ethanol is more volatile than gasoline and vaporizes at lower temperatures.

I've inspected all of them and found no evidence of leakage. I began to notice this phenomenon around the time Atlanta was mandated to sell ethanol-laced fuel 8 years ago or so.

It's most prevalent after the vehicle is driven or sometimes on very hot days. It's most noticeable around my '79 F100 ( I think because it has an open element air cleaner) but my '56 Cadillac is close behind.

By all means check everything possible but don't pull your hair out if nothing turns up.

Having said that, I did have a problem with the '66 Toro soon after I bought it. Someone had installed a vented gas cap. The manual specifically states to use a non-vented cap. When parked, fuel was rising up the filler neck and forcing its way out of the cap. The correct non vented cap solved that immediately.

[68 Toro]

Thank you kindly for the suggestions. I will look into all of these possibilities and report back.

[Doc Hubler]

These tanks are vented. On warm days, you'll smell a little fuel -- you should. You don't want much air in your tank, as there is a certain fuel/air ratio that becomes explosive (there is a specific range). Having said that, it's highly unlikely you would get to that specific range, since you're unlikely to fill most of your tank with air. The vapor pressure of the fuel constantly pushes out of the tank, preventing much air from coming in. I know these vent lines are the same on the 66-67 cars. Not sure how they changed for 68. There are two lines -- one from each side of the tank baffle for 66-67 and they exit out the rear near the license plate door. There are filters in the ends of the vent tubes. I know they changed the tank sender unit in 68. Those have electrical current flowing through them. important to not have a fuel/air mixture that could cause a tank explosion (electrical spark could always be an ignition source). When you fill your tank with gas, of course, some air goes in the tank, but relative to the fuel vapor, the ratio isn't anywhere near explosive range. Good reason to always shut the ignition off when fueling however. Fuels have ethanol in them today which has a higher vapor pressure than the basic hydrocarbon compoenents; so it's not surprising you may notice the odor. And I don't care how airtight your lines are, you'll always have some fuel vapor from the carb area. Driving modern cars with their designs today, most of this has been eliminated to prevent air pollution. I know I'm always much more aware of fuel odors on older cars these days as my modern daily driver burns more efficiently and clean with essentially no odor.

[Otto Skorzeny]

Here is a description from the factory service manual.

The fuel tanks used on 94 and 96 Series have a capacity of 24 gallons with a fuel filler pipe located behind the license plate. Venting of the tank is provided using a hose and pipe routed up through the floor pan in the rear compartment and back down through the floor pan grommet terminating behind the right rear coil spring seat. A baffle is positioned laterally in the tank to stabilize fuel level and minimize noise. A non-vented gas cap is used.

[68 Toro]

The fuel filler cap on my Toronado has the following text in large, raised, block letters:

NOT VENTED

The fuel-like odor that I detect during warm and hot weather is different than that from gasoline. I suppose vaporized ethanol is the most likely source, though I wonder why it is so noticeable inside the passenger compartment.

[Otto Skorzeny]

They weren't exactly building these crates air tight back then like cars today. Smell is probably coming through the firewall or through the rear package tray or back seat. I just noticed you're in Miami so the warm, hot day phenomenon is pretty much all the time, eh?

[68 Toro]

Yeah except for a few days in January, or when a polar vortex hits us.