US Patent 7717092 Fuel system with air venting and fuel anti-drainback

A fuel system of an engine is provided with a venting assembly to vent air that accumulates within a fuel filter of the fuel system and provides anti-drainback of clean fuel back toward the fuel filter when the engine is turned off. In one embodiment, the venting assembly includes a piston valve that provides both the vent and anti-drainback. The valve is actuatable by fluid pressure to a first position that restricts drainback, a second position that restricts venting, and intermediate positions between the first and second positions which permit venting.