Alcohol-in-fuel can be detrimental to the fuel system components. Alcohol-in-fuel may cause driveability problems such as hesitation, lack of power, stall, no start, etc.

Fuel system corrosion and subsequent fuel filter plugging, deterioration of rubber components and/or air fuel mixture leaning may cause the problem.

Various types and concentrations of alcohol are used in commercial fuel. Some alcohol is more detrimental to fuel system components than the others. If you suspect an excessive amount of alcohol in the fuel as the cause of a driveability condition, use the following procedure in order to detect the presence of alcohol in the fuel. This procedure uses water in order to extract the alcohol from the fuel.

Draw the fuel sample from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy, or contaminated with water (as indicated by a water layer at the bottom of the sample), do not use this procedure, and clean the fuel system.

1. Using a 100 ml cylinder with 1 ml graduation marks, fill with fuel to the 90 ml mark.
2. Add 10 ml of water to bring the total fluid volume to 100 ml and install a stopper.
3. Shake vigorously for 10 to 15 seconds.
4. Carefully loosen the stopper in order to release pressure.
5. Close the stopper and shake vigorously again for 10 to 15 seconds.
6. Put the graduated cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer (which would now contain both alcohol and water) will be greater than 10 ml.

For example, if the volume of the lower layer is increased to 15 ml, it will indicate at least 5 percent alcohol in fuel. The actual amount of alcohol may be somewhat greater because this procedure does not extract all of the alcohol from the fuel.