Patent ID: 8006674

Claim:
A engine fuel system, comprising: a fuel tank having a vapor dome above a fuel level; an engine manifold; a valve disposed between the fuel tank and the engine manifold, the valve including a fuel tank passage for communicating with the vapor dome in the fuel tank, an engine manifold passage for communicating with an engine; a first cavity coupled with the fuel tank passage and the engine manifold passage to form a vapor flow path between the fuel tank and the engine manifold, the cavity having an atmospheric pressure vent, the first cavity having a first orifice venting the first cavity to the atmosphere to keep the pressure in the cavity at atmospheric pressure; a second cavity separate from the first cavity and tank passage, the second cavity having a second orifice directly vented to the atmosphere: a check valve that selectively allows atmospheric make-up air from the second orifice to enter the tank through the tank passage: and a pressure-responsive valve member disposed in the first cavity, the valve member using atmospheric pressure as a reference and being movable between an open position that allows vapor flow between the fuel tank passage and the engine manifold passage when pressure in the tank is above atmospheric pressure and a closed position that blocks vapor flow between the fuel tank passage and the engine manifold passage to isolate the vapor dome in the fuel tank from the engine manifold when pressure in the manifold passage is below atmospheric pressure, wherein the manifold passage provides a direct vapor flow path between the valve member and the manifold.