a fuel pump body has a chamber with one wall formed by an external diaphragm having a stem connected thereto . the fuel pump body is attached to the outside of a valve cover for a gasoline engine and the valve cover has a depression that forms an enclosure for the diaphragm . the stem passes through an aperture in the valve cover and connects to a lever pivotally attached to the underside of the valve cover . the lever engages the valve rocker arm of the engine and produces reciprocal movement of the stem and diaphragm as the rocker arm moves . the reciprocal movement of the diaphragm alternately draws fuel into the chamber through the inlet and that expels fuel through the outlet .