Evaporative Emissions System: Testing and Inspection

DESCRIPTION
Alcohol-in-fuel can be detrimental to fuel system components and may cause driveablity problems such as hesitation lack of power, stall, no start, etc. The problems may be due to fuel system corrosion and subsequent fuel filter plugging, deterioration of rubber components and/or air-fuel mixture leaning.
Various types and concentrations of alcohols are used in commercial fuel. Some alcohols are more detrimental to fuel system components than others. If an excessive amount of alcohol in the fuel is suspected as the cause of a driveablity condition, the following procedure may be used to detect the presence of alcohol in the fuel,

TESTING PROCEDURE
The fuel sample should be drawn from the bottom of the tank so that any water, if already present, can be detected. The sample should be bright and clear. If the sample appears cloudy or contaminated with water as indicated by a water layer in the bottom of the sample, this procedure should not be used. The fuel system should then be cleaned.

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 and release the pressure.
5. Close the stopper and shake vigorously again for 10 to 15 seconds.
6. Carefully loosen the stopper to release the pressure.
7. Put the graduated cylinder on a level surface for approximately 5 minutes to allow time for adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer (which would now contain alcohol and water) will be greater than 10 ml. For example, if the volume of the lower layer is increased to 15 ml it would indicate at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat greater because this procedure does not extract all of the alcohol from the fuel.