This injection pump washer, also referred to as a gasket, seals the interface between the injection pump and its mounting surface on the engine. It prevents fuel or oil leakage and maintains the correct clamping force on the pump housing. A degraded or missing washer allows air ingress into the fuel system, causing hard starting and erratic engine operation. This component is manufactured by AGCO to the original thickness and crush characteristics, ensuring the pump sits at the correct depth relative to the drive gear. On reinstallation, clean both mating surfaces and replace the washer; do not reuse the old one.