The scenario is something like this: Your tractor is running perfectly, you finish your job and park it in the shed. A few weeks go by as life happens, or if you are like me, you have other tractors to use and spread around time between all of them. You come back to your perfectly running tractor, attempt to start it, and either it doesn't run, or it coughs and starts only to die and then won't even fire. You let it sit for a few minutes, and get a false hope when it seems to start, only to be let down when once again it dies. You may be experiencing the problem with putting ethanol in the tank of an engine that doesn't get continuous use.
We live with Alcohol in our Gasoline now as a norm. This has some negative and positive elements to it. None of the positives scale to small engines or larger engines that normally sit for periods of time. The costs and waste in maintenance overrides any benefits that may result from using fuel containing alcohol. For those of us with a farm that may have 20 gasoline engines for special purposes that get used at best every few days, the negatives abound. You can't keep any of your important engines in functional condition. Some, may require rebuilding the carb every time you need it. In my experience, using a pressure washer, means a day to remove the carb, get your carb kit, run the carb through ultrasonic, rebuild and install it, and only then can you actually use your pressure washer. The same holds true for a lot of tractors depending on how consistently you use them.
Our blended gas is really only good for a few weeks at most. Then you start feeling the effects of it's change. Alcohol attracts water, it pulls it out of the air... water and the metals in your engines and tanks, is not ideal. Every time I pull apart one of my now dysfunctional carbs from Ethanol, the carb will have a sickly looking corrosion that has to be removed. Additionally, alcohol can dissolve sludge that was created by gasoline in the first place, so the gas residue that was happy to remain where it was, becomes free and moving through your fuel system. That sludge has to go somewhere when it dissolves, and those tiny orifices in the carb are a perfect place for them to find a new home.
Suffice it to say, if you put gasoline laced with alcohol in your tractor or small engine, it either must be used up quickly, a few days at best, or you have to take steps to somehow stabilize it. The best case is if you have a local source that sells non-ethanol gas, buy it, because basically our seldom-used engines are not compatible with ethanol. But finding non-ethanol may not be possible, and the next best thing is to use a well tested gas stabilizer the mitigates the problems with ethanol storage in our gas cans, gas tanks and carbs. We sell a good stabilizer as do many places, it's not hard to find.
The fact is, ethanol isn't the only reason we clog up our carbs so often, no gas sitting in a carb is going to last forever, and some tractor enthusiasts don't use their restored tractors, so they are going to sit for long periods of time. A couple of simple steps can help quite a bit. Here is my list of what I do, even if I use non-ethanol gas.
My old tractors and small engines on the farm, do not get turned off with a key switch. I shut off the gas at the sediment bowl or fuel shutoff and let them run out, then shut off the switch. If there is a drain on the carb, I drain it after the engine cools, and put that gas in my car or truck where I know it's going to be used before it goes bad. Then there is refilling the tank to the brim. This will make sure there is the minimum surface area of fuel exposed to the atmosphere. Now especially with ethanol, that surface area is where it will go to draw the water out of the air. These steps increase my confidence that when I return to the machine, I will be able to use it rather than work on it.
As a postlude to the above, there is one other issue with ethanol that makes it important to completely drain all of it after every use. This doesn't apply to old tractors, but it does apply to some small engines a farm may have. I'm talking about two stroke engines like chain saws, and four strokes like small weed eaters, trimmers and even most 5 to 10 horse engines on other small single purpose devices. If the carb or storage has some rubbers and plastics, those will self-destruct when soaked continuously in ethanol. We would hope that manufacturers will change the composition of materials to counter this, but at present, even relatively recent engines will fall victim to this. When this happens, it's not a simple carb cleaning and rebuild, it's a carb replacement. A chain saw carb can run over one-hundred dollars. There is almost no choice but to make sure you put such engines away bone dry.