A non-pressurized fluid level shutoff system for a fuel tank includes a fuel receiver having a flow control valve that opens in a direction opposite a direction of fuel flow, and that cannot be manually overridden. A fuel sensor funnels fuel through a fuel jet outlet orifice to form a stream of fuel across a cutout section, and a supplemental peripheral port connected between an outlet orifice mixing chamber and the interior of the tank is oriented perpendicular to the stream of fuel across the cutout section, to interfere with the stream of fuel when the sensor is submerged in fuel in the tank, to further reduce any residual fluid flow signal when the sensor is fully submerged, allowing the flow control valve in the receiver to close completely.