Gas evaporating?

gtoman

New User
If my tractor is not used for a few weeks, I notice that some of the gas has disappeared. When it sits idle for the winter months, the tank will be empty of gas, but I think it still contains water because I had a problem with water in the gas the first time I used it this Spring. It sits in my enclosed garage and I do not notice the smell of gas or see signs of a gas leak. The cork seal in the tank cap is dried up. Is it possible that the gas is evaporating thru the top of the tank? It seems that if I had a very slow tank leak, the water in the tank would also be leaked out also when Springtime arrived.
 
(quoted from post at 23:46:54 09/10/18) If my tractor is not used for a few weeks, I notice that some of the gas has disappeared. When it sits idle for the winter months, the tank will be empty of gas, but I think it still contains water because I had a problem with water in the gas the first time I used it this Spring. It sits in my enclosed garage and I do not notice the smell of gas or see signs of a gas leak. The cork seal in the tank cap is dried up. Is it possible that the gas is evaporating thru the top of the tank? It seems that if I had a very slow tank leak, the water in the tank would also be leaked out also when Springtime arrived.
ou didn't give a tractor model, but virtually all older tractors had vented vs sealed tanks (gravity feed does not work sealed) and so , yes it will evaporate. I try to keep my seldom used equipment topped off with ethanol free gasoline (or diesel) and find that I need to add a quart or so every month or two. No leaks, just evaporation.
 

Yes, it evaporates. However, if you fill it very close to full, or right up to full with warm gasoline, there will be less surface area exposed so evaporation will be much slower.
 
(quoted from post at 08:50:45 09/11/18)
Yes, it evaporates. However, if you fill it very close to full, or right up to full with warm gasoline, there will be less surface area exposed so evaporation will be much slower.

Don't know what kind of tractor you have, but have you checked the oil level.
Bad things can happen......don't even ask how I know.
 
just to add to what these guys said.. if your gas was ethanol gas, AND you see free water in your tank, then you have a HUGE
water issue, as ethanol gas will naturally absorb SOME free water anyway.. if you see water at the bottom of a tank with ethanol
gas in it, then the e-gas is saturated..
 
(quoted from post at 06:10:04 09/11/18)
(quoted from post at 08:50:45 09/11/18)
Yes, it evaporates. However, if you fill it very close to full, or right up to full with warm gasoline, there will be less surface area exposed so evaporation will be much slower.

Don't know what kind of tractor you have, but have you checked the oil level.
Bad things can happen......don't even ask how I know.

This was my thought, also. Stale gas can push the float valve open, overflowing the the float bowl, then thought the intake manifold, into the cylinders, and through the ring gaps to the crankcase then the oil pan.
 
(quoted from post at 06:10:04 09/11/18)
(quoted from post at 08:50:45 09/11/18)
Yes, it evaporates. However, if you fill it very close to full, or right up to full with warm gasoline, there will be less surface area exposed so evaporation will be much slower.

Don't know what kind of tractor you have, but have you checked the oil level.
Bad things can happen......don't even ask how I know.

This was my thought, also. Stale gas can push the float valve open, overflowing the the float bowl, then thought the intake manifold, into the cylinders, and through the ring gaps to the crankcase then the oil pan.
 
(quoted from post at 20:01:31 09/11/18) Did you try shutting the fuel petcock every time you park it?
Thanks for all the responses. I failed to mention the tractor is a 1960 Ford 601 Workmaster. I do turn the full line cut-off to the off position each time I stop using the tractor, but at the beginning of Winter I have not been filling the tank completely full. Different folks have different opinions about that one. I saw one video re: Winter storage which said empty the tank but run a small amount of race car fuel into the carb. He was in Michigan. I will check the oil for signs of water the next time I go down to the farm.
 
We were suggesting that you check the oil level to see if fuel had drained into the crankcase, increasing your oil level. Checking for water is good, too, though. Smell of it and see if it smells of gasoline, also. If you're closing the petcock as you said I imagine this will not be a problem.
 
(quoted from post at 10:47:18 09/12/18) We were suggesting that you check the oil level to see if fuel had drained into the crankcase, increasing your oil level. Checking for water is good, too, though. Smell of it and see if it smells of gasoline, also. If you're closing the petcock as you said I imagine this will not be a problem.

So since I have a vented cap, it sounds like some evaporation is bound to happen. When putting the tractor aside for the Winter months, I wonder if filling up the tank with non-ethanol gas and using a non-vented cap(if there is one available) while it sits in the shelter during the Winter would solve the evaporation/condensation problem????
 
marine sta-bil will reduce the evaporation and keep it from absorbing water (as fast).

from what i understand the sta-bil leaves a film of oily substance on the surface that prevents moisture from soaking into the gas and gas from evaporating.

also just generally a good idea for any of these old engines to have it, although, i left a truck sit up for 2 years and the gas went bad even with sta-bil in it, so its not a miracle cure.

i think its best to only put as much gas in as you will use in a few months, if you only go through a gallon a year, having 3 gallons of 2 year old gas sitting in there will cause more problems than keeping it topped off will solve.
 
How much do you use this tractor? If you're not using it enough to run a few tanks through it a year, you need to add fuel stabilizer, I like Sta-bil, and keep the tank full. That will solve your water problem and keep your gas from going bad.

If you run two or three tanks through it a year, I'd only add the stabilizer in the winter when it's not used for several weeks at a time. If this is what you do, before you set it up for the winter, shut the petcock off, add the stabilizer to the tank, then drain the carb. Open the petcock up and run it for a while to make sure to get some treated fuel in the carb.

If you keep the tank full, the cap's not going to matter.
 

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