Abstract: A system for regulating fuel flow in a fuel line from a supply of fuel to an engine, comprising: a fuel regulator disposed in the fuel line intermediate of the engine and the fuel supply regulating the flow of fuel to the engine; vacuum lockoff apparatus, disposed in the fuel line intermediate of the fuel regulator and the fuel supply and connected to the engine by an air passageway, sensing a partial vacuum condition at the engine, the vacuum lockoff means allowing flow of fuel in the fuel line when a partial vacuum condition is sensed and prohibiting flow of fuel in the fuel line when the partial vacuum condition is no longer sensed; one way check valve, disposed intermediate of the engine and the vacuum lockoff means in the air passageway, maintaining partial vacuum condition at the vacuum lockoff means; and bypass valve means, connected to the air passageway so as to provide an air passageway bypassing the one way check valve, for allowing restricted flow of air to the vacuum lockoff apparatus whereby the