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Ethanol Fuel Problems Including Solutions

Carbureted engines, like those used in outdoor power equipment are not designed for gasoline with greater then 10% ethanol (such as E15, E20 and E85); using higher ethanol fuel blends may lead to engine damage and/or performance issues. Carburetors lack the ability to automatically adjust to the performance differences between Gasoline and Ethanol. 

During periods of extended storage, ethanol draws in atmospheric moisture which can lead to a build-up of water in the carburetor bowl and fuel tank. Since the carburetor is vented and the moisture in the air is being taken up by the ethanol, new air brings more moisture through to the vent every day as the air temps rise and fall. Inside the carburetor bowl, because the density of water is greater than gasoline, the ethanol/water mixture separates from the gasoline and settles to the bottom of the bowl. 

Phase Seperation
Jet Size Compare

This is referred to as “Phase Separation” and because the fuel pick-up inside the carburetor bowl is located on the bottom, the first thing sucked up through the jets is the ethanol/water mixture. The water sent to the engine causes poor performance, higher engine temperatures and vital parts damage. 

The ethanol / water mixture at the bottom of the carburetor bowl and in the fuel tank also causes internal parts corrosion. The jet which is a very small hole drilled in a piece of metal (usually brass) is what allows a very precise amount of fuel into the engine. This is at the bottom of the fuel pickup and can be sitting in the Ethanol/Water mix at the bottom of the bowl. In a very short amount of time that tiny passage becomes closed due to corrosion, causing engines to not start or be very hard to start. Other components such as float valves and air passages can also corrode shut or open from the excess moisture. 

On the other hand, the ethanol and water mix in gasoline is a breeding ground for microbes like bacteria and fungi which just adds to the corrosion and debris inside the carburetor bowl. These deposits clog the carburetor jets and fuel and air passages inside the carburetor which is main reason why the engine won’t start or operate poorly.

Even if the engine is run dry at the end of the season, there will still be some fuel left in the carburetor. This turns to gum and varnish and dirt and restricts the passages inside the carburetor.

It is impossible to empty all of the fuel from any engine system so there is always old fuel somewhere in the fuel system and inside the carburetor.