overview Aftermarket lift pumps provide more fuel to your dies el engine but face issues at a 1/4 tank fuel level. The S&B Sending Unit allows you to drive to empty with your pump. Completely plug and play, with no need to modify your OEM tank or sending unit. *For use with aftermarket lift pumps only. DRIVE TO EMPTY. NO MORE LOW FUEL LEVEL ISSUES. The S&B Sending Unit uses a Venturi Jet Pump powered by your aftermarket external lift pump to keep the reservoir full, even with extremely low fuel levels in the tank. A full reservoir means fuel to your engine and no check engine lights!