These BD Diesel lift pumps are designed to replace your stock lift pump. The stock lift pump is barely adequate for the stock engine, so when you start adding the latest in performance electronics or bolt-ons, it can soon be overwhelmed by fuel demand, placing additional strain on the injection pump. It is designed to bypass/eliminate the use of the stock pump on the motor. The BD Diesel lift pump mounts directly on the frame rail with all the supplied hardware and wiring harness that plugs directly into your factory harness. The pump mounts directly on the frame because it's easier for the pump to push fuel rather than pull it from the tank and the vibrations from the motor shorten the life of the pump when it's mounted on the engine.