Patent ID: 7216635

Claim:
A method of delivering fuel from a fuel tank in fluid communication with a float bowl carburetor of an internal combustion engine, so as to mitigate evaporative emissions of said fuel from at least one of said fuel tank and said float bowl carburetor, said method comprising the steps of: (a) containing said fuel within said fuel tank, said fuel including liquid fuel and fuel vapors; (b) during operation of said internal combustion engine, permitting fluid communication of said liquid fuel between said fuel tank and said float bowl carburetor, and permitting outward venting of said fuel vapors from said fuel tank through a diaphragm-type pressure relief valve substantially only when pressure within said fuel tank exceeds a predetermined threshold superatmospheric pressure greater than three psi therein; and (c) during inoperation of said internal combustion engine, preventing fluid communication of said liquid fuel between said fuel tank and said float bowl carburetor, and permitting outward venting of said fuel vapors from said fuel tank substantially when pressure within said fuel tank exceeds a predetermined threshold superatmospheric pressure therein.