Gasoline Disappearing from Tank ... Evaporation?

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clifftt

clifftt

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I have a fuel gauge issue to be resolved later. In the meantime, I write down how much gas I pump in my car, ‘66 Barracuda, and the odometer reading. Last August, I put 7 gallons of gas in it, drove about 30 miles. In October, went on a short drive, and found car running out of gas.
I added 3 gallons, and drove 11 miles. Now in July, same thing happens, running low on gas, barely made it home.
Car is always inside a locked garage. No fuel leaks, no odor of gas in the garage. Original tank with new filler hose, original gas cap, using an Eddy carb.
I did not see this subject here on FABO, but did over on H.A.M.B.:

“A few months ago I put 3 gallons of gas in a project car's dead-empty and recently cleaned gas tank. The car has been started about a dozen times and run around the block about a half dozen times, a total of less than 4-5 miles driving. Last night it ran out of gas on a test run. The car has a vented cap and I'm thinking that quite a bit may have evaporated away. “

Anybody here share my problems?
 
My dart sat for 4 years and had 1/2 tank in it when I started it. If it evaporaated as fast as your thinking I suspect it would have been empty. I don't know how much was in the tank when it was parked.

My guess is that you are burning way more fuel than you think you are. Fill the tank, record your mileage (assuming you odometer is accurate) and go for a long drive or a bunch of short drives in one day 100 miles will do. ( 3-4 hours of city driving at 25-40 miles per hour) then refill the tank. wala miles per gallon.
 
I can't speak to all your problems, but I can tell you what happened when you put 3 gallons in an empty tank. I did some testing on my 67 Barracuda gas tank. When I put gas in an empty tank, the float did not move and the pick-up screen did not get covered until about 3.5 gallons. So, the first 3 gallons don't count and are not usable.
 
Boy, there sure is a lot of gas disappearing around here. This is the second thread in a day or so. :lol:
 
clifftt said:
I have a fuel gauge issue to be resolved later. In the meantime, I write down how much gas I pump in my car, ‘66 Barracuda, and the odometer reading. Last August, I put 7 gallons of gas in it, drove about 30 miles. In October, went on a short drive, and found car running out of gas.
I added 3 gallons, and drove 11 miles. Now in July, same thing happens, running low on gas, barely made it home.
Car is always inside a locked garage. No fuel leaks, no odor of gas in the garage. Original tank with new filler hose, original gas cap, using an Eddy carb.
I did not see this subject here on FABO, but did over on H.A.M.B.:

“A few months ago I put 3 gallons of gas in a project car's dead-empty and recently cleaned gas tank. The car has been started about a dozen times and run around the block about a half dozen times, a total of less than 4-5 miles driving. Last night it ran out of gas on a test run. The car has a vented cap and I'm thinking that quite a bit may have evaporated away. “

Anybody here share my problems?
Click to expand...

This is an easy one.
Not only do you not drive that car enough, you also don't put enough gas in it.:D
Each makes the other worse.
 
TrailBeast said:
This is an easy one.
Not only do you not drive that car enough, you also don't put enough gas in it.:D
Each makes the other worse.
Click to expand...
I remember a time when gas prices shot up and reading that a full tank means less evaporation. I don’t understand why, but I suspect this might be true.

Since this is still a “project car”, I didn’t want to fill it with gas and have it spoil over time. Just gonna have to get it out on he road more often.
 
clifftt said:
I remember a time when gas prices shot up and reading that a full tank means less evaporation. I don’t understand why, but I suspect this might be true.

Since this is still a “project car”, I didn’t want to fill it with gas and have it spoil over time. Just gonna have to get it out on he road more often.
Click to expand...

I believe that is true also, due to more air area inside the tank allowing quicker evaporation.
 
Reformulated, aired up, watered down, ethanol-ed, who knows what's coming out of these pumps.

krazykuda said:
I'm sneaking around and siphoning it out on you little at a time.... :D
Click to expand...

Lol, What movie was it pranksters were adding gas to a guys car and he was raving about of the exceptional mileage he was getting, then they started siphoning some out?

Did you say 7 miles to a gallon or was the 7 gallons to a mile?

That 1966 32¢ / gallon gas probably lasted a little longer.

FWIW...…..

 
Check your engine oil. Is it magically fuller? Does it smell like fuel or seem thin?
 
Shitty modern fuels full of ethanol. It turns to vapor easier than gasoline..... thus the many vapor lock issues. Try running real 100% gasoline and see if it is better. In these parts the only real gasoline you can buy with no ethanol (other than avgas or race fuel) is Chevron 94 octane.
 
When I first filled up my 65 Barracuda at a gas station and drove it home, people honked at me and said I was leaking gas. Sure enough, gas was sloshing out of the filler or vent tube. The gas cap had no seal. I made a seal for the gas cap. I think this solved the problem, but I never fill the tank up fulL so I can't say for sure. Maybe someone else can explain what's going on with the vent tube.
 
jos51700 said:
Check your engine oil. Is it magically fuller? Does it smell like fuel or seem thin?
Click to expand...
Thank goodness, jos, the oil is clean, no gas odor.
d55dave said:
Shitty modern fuels full of ethanol. It turns to vapor easier than gasoline..... thus the many vapor lock issues. Try running real 100% gasoline and see if it is better. In these parts the only real gasoline you can buy with no ethanol (other than avgas or race fuel) is Chevron 94 octane.
Click to expand...
d55, no ethanol sold in the Bay Area that I’m aware of, unless somehow they are mixing it in. Pumps and signs have no mention of ethanol.
RichB, that’s another reason I don’t fill it. I did however, buy Slantsixdan’s gas cap. I haven’t put it on yet, now’s a good time to test it.
I think what Beast is describing is what’s going on. If anything else comes up, I’ll report it.
Thanks all for your replies.
 
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