An GM Genuine Mechanical Fuel Pump is a GM-recommended replacement for your vehicle’s original components, and is a diaphragm positive displacement pump. A rocker arm driven off the fuel pump camshaft lobe moves the diaphragm, causing fuel to be drawn in through a one-way inlet reed valve. As the cam lobe rotates away from the rocker arm, a spring pushes the diaphragm back, pushing the fuel out through a one-way outlet reed valve to the carburetor. This original equipment fuel pump has been manufactured to fit your specific GM vehicle, providing the same performance, durability, and service life you expect from General Motors.