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Fuel Shut off Valves and failed Floats

Version 0.0

December 20, 2015

Presented by:

Raymond VanDervort


Bowl Type Carburetors usually found on most 4 cycle engines. Additional scope may include various other fuel systems.



First to prevent leak and fire hazards, second to minimize storage deterioration within the carburetor forcing service and preventing proper operation of the engine. 


Much equipment is sold without a shut off valve or one not best placed.  Second, all bowl float carburetors can occasionally leak fuel, particularly if feed fuel by the most common method of gravity. In such a design, the only thing preventing fuel from leaking is the inlet needle in the bowl float carburetor.


Simple improvement in many cases is to install a fuel shut off valve in the fuel feed system to the carburetor. The best location is one that threads into the tank, but this is not always easily done, and nearly as good is a n inexpensive in-line shut off valve. 


Customer usage:

Upon completion of equipment usage, we recommend shutting the valve off and letting the equipment run out of fuel, thus the carburetor has little fuel in it and cannot get more if it were to leak and also will have less fuel exposed to air, as the bowl is vented and the gas in the bowl that remains will deteriorate. When next used, the fresher fuel bottled up in the fuel line will dilute the remnant fuel in the bowl, making the mixture a better fuel source than if this procedure had not been done.  This equates to less service, better starting, more reliable, cleaner running, less pollution, less fire hazard.


Equipment that is transported:

All Commercial Outdoor Power Equipment transported on a trailer or vehicle should have a shut off and it should be used. In some cases, gas dilution of the oil when a leak occurs will result in engine damage on the next run. Even if this does not occur, in the life of a unit a leak will occur, possibly on most relocations, causing a loss of costly fuel.