This causes some engines to run rough. Also, engines may run hotter on lean mixtures, which, in the extreme, can result in engine damage. If the engine in your equipment is running rough and it has an adjustable carburetor, check that the adjustment is proper for the fuel you are using. Either contact a knowledgeable serviceman or follow the manufacturer's instructions in your owner's manual. Consult your authorized dealer or serviceman about the manufacturer's recommendations for your engine model and year.
Vaporization prevents the fuel pump from delivering sufficient gasoline to the engine.
Factors favoring vapor lock are high ambient temperatures which accompany high power output. Sometimes vaporization occurs after the engine has been intentionally stopped because of the cessation of mechanical cooling and fuel flow. In this case, the hot engine will be difficult to start. Vapor lock and hot restarting have been reoccurring problems for engine manufacturers. Some manufacturers are concerned that oxygenated gasoline will aggravate these problems because adding either ethanol or MTBE to gasoline increases volatility.