Becoming less depend ant on foreign oil is a good thing. I believe it has to happen. This is in no way meant to be an argument against alternative fuels of any kind. As the blending of alcohol with gasoline is becoming more common and the percentage of alcohol in gasoline is getting higher outdoor power equipment has begun to pay the price.
I would say nearly 90% of what we see in our shop on a daily basis follows this scenario. A piece of equipment will come in, the complaint on the tag is “won’t start”, “doesn’t run right”, or maybe “there’s gas in the crankcase”. We find the carburetor to be malfunctioning. On the easy ones, a good cleaning and fresh fuel gets things working again. If the equipment is still under warranty there can be hurt feelings. Manufacturer’s Warranties only cover defects in material and workmanship of the equipment , the fuel itself is at fault here.
Many of the manufacturers approve the use of fuel with up to 10% ethanol. Most gasoline sold in the US has some alcohol in it. Engines will run on this fuel however care must be taken in its storage. Properly blended fresh fuel works fine, time and environment can change that.
I am not a chemist, the following information was given to me by people I trust. Alcohol attracts moisture. The region where I live normally has a humidity level above 50%. This means there is available water vapor in the air. It is drawn to the alcohol and absorbed. As the amount of water in the fuel increases, it and the alcohol become separated from the gasoline and settle toward the bottom of the tank or carburetor bowl. The gasoline also deteriorates over time until performance becomes degraded. Our technical advisers tell us not to by any more fuel than we can use in 30 days. It can go bad that fast.
This is what I see on a daily basis. There is water in the fuel system. Water will not burn. This is the most common reason an engine won’t start. All we have to do is drain the water and get fresh fuel into the engine, now it starts. Unfortunately, it gets worse from here. If the water has been allowed to sit for any period of time, such as during winter storage, there will be corrosion. Most fuel tanks are now made of plastic so they are not the problem. There are only a few plastic carburetors at this time, most are some form of metal alloy. When this alloy oxidizes, the very small passages in the carburetor become blocked. Sometimes this corrosion can be flushed from the passages, if it is very bad it can not and a new carburetor will be needed. We also are finding more occurrences of a thick black sludge in the carburetor bowl. This is from the alcohol dissolving the inside of the fuel lines.
People seem to get offended when I tell them there was water in their fuel. “I keep my can and my mower in the garage out of the rain.” So do we, there is water in our cans regularly. I believe there is water in the fuel we buy. Another statement I hear regularly is, “It runs just fine in my car.” You have to remember, car manufacturers have been working toward alcohol blended fuels since the 70s. They have alcohol resistant hoses and seals, lawnmower engines do not. Computer controlled engines can also adapt to poor running conditions, while there are only a hand full of large commercial mowers that are electronically fuel injected.
Adding one of the popular fuel additives designed to disperse water will do just that to the fuel in the tank. The brands I have looked at use alcohol to accomplish this, if the fuel is not used quickly you will be back in the same situation. I have never been able to get the additives to remove water that has made it to the carburetor bowl, it just can’t get in there. The carburetor needs to be disassembled and flushed out. I prefer to prevent it rather than fix it. I don’t buy any more gas than I will use immediately. I also don’t pour the last bit of gas from the can into my mower (the bottom is where the bad stuff lives).
If you have to remove water from the fuel system of your mower, check your can before adding gas. Don’t pour the same gas from the same can that you used last time into your mower. Odds are that is where the water came from and your engine won’t run for very long.
2-cycle engines face additional problems. The water and alcohol can prevent the oil from mixing with the fuel properly. More than 20% percent alcohol in fuel will wash lubricating oil from the cylinder walls. Either situation can result in catastrophic failure of the engine.