Mechanical fuel pumps are commonly found on carbureted gas engines and diesel engines. These pumps are operated by the engine's camshaft or crankshaft. As the vehicle's speed increases, the amount of fuel pumped to the engine also increases. If your engine misfires, hesitates, or stalls, it may have a failing fuel pump and should be replaced. If the pump fails, the vehicle will not run. O'Reilly Auto Parts carries replacement mechanical fuel pumps to get your vehicle back on the road.