This manual fuel pump is a positive-displacement feed pump for the fuel system. It draws fuel from the tank and delivers it to the injection pump, maintaining a steady supply to the high-pressure side of the engine. The pump is hand-operated, allowing the system to be primed after filter changes or maintenance. A worn or leaking pump allows air ingress, causing hard starting and erratic engine operation. The manufacturer machines the pump body to match the original mounting flange and plunger bore, so the stroke volume and priming pressure replicate the original assembly. On installation, ensure the pump lever is in the correct orientation for the host engine and that all banjo fittings are sealed with new copper washers.