Make your own free website on

"The Lawn Mower Repair Man's Front Page"

"Vapor Lock"


If you have an unexplained engine stallng or quiting after running long enough to warm up the engine and the problem doesn't exist in cooler weather, think about this.

It may not be all that popular to mention with fuel prices being as criminal as they are but during warm weather the simple fix may be as easy as switching to a premium grade of fuel and not from the local discount outlet. All fuel today is formulated for rapid vaporization for better emission control but this can be a hanging point for small air cooled engines. The high heat and vibration causes more rapid vaporization, coupled with the higher ambient heat of summer and you can get excessive air pockets in the fuel system which creates a vapor block of fuel flow.

Because premium fuel uses more expensive ingrediants to formulate the correct properties it is less likely to cause a vapor lock condition. Your engine may not need the higher octane but the fuel system may benefit from the premium quality. Also, premium actually runs an engine slightly cooler due to a better controlled burn cycle.

Naturally, it is very important to give your engine every advantage in warm weather by maintaining all that should be. Keeping the cooling fins cleaned out of debris build up is often overlooked. Proper oil level and oil quality. Avoid multi-viscosity oils in warm weather, stick with straight 30wt and keep it clean. Fresh fuel, less then 30 days old. This not only eliminates the use of fuel that isn't as good as it should be but also provides the most recent temperature/seasonal formulation from the refinery.
LMRM;Bob :<=

T.O.M. Archives-- Front Page-- Back to Message Board

"The Lawn Mower Repair Man's Front Page"