Importance

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Abstract

The present invention provides an evaporative emissions control system for small internal combustion engines. The fuel tank of the engine includes a filler neck closed by a fuel tank cap which seals the fuel tank in a manner in which air and/or fuel vapors are not permitted to pass between the filler neck and the fuel tank cap. The fuel tank cap includes a first, one-way vacuum relief valve therein which operates to allow atmospheric make-up air to enter the fuel tank to replace a decreasing amount of fuel in the fuel tank during running of the engine, or otherwise as needed. The fuel tank cap additionally includes a second, one-way pressure relief valve having a first cracking threshold which operates to relieve high pressures within the fuel tank. Additionally, the fuel supply line between the fuel tank and the carburetor includes a fuel flow inhibiting or blocking member having a second cracking threshold greater than the first cracking threshold of the pressure relief valve of the fuel tank cap. In operation, fuel vapors are sealed within the fuel tank at all times when the fuel tank cap is closed to prevent fuel vapors from escaping into the atmosphere, and the fuel flow blocking member prevents flooding of the carburetor with liquid fuel if the fuel vapors within the fuel tank build to a high pressure prior to cracking of the pressure relief valve of the fuel tank cap. When the fuel tank cap is removed, a vapor vent valve in communication with the vapor dome of the fuel tank is opened, allowing vapor pressure to be relieved prior to disengagement of the fuel tank cap from the filler neck.

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First Claim