This fuel injector delivers a metered charge of fuel into the engine cylinder at the correct pressure and timing for combustion. It is a complete assembly, including the nozzle and internal valve components, and mounts directly into the cylinder head. The injector opens when fuel pressure from the injection pump overcomes the spring force inside the body; a worn or sticking injector causes misfiring, rough idle, and reduced power output. As an original-manufacturer component, the injector body and nozzle are matched to the cylinder head bore and sealing washer thickness, which maintains the correct compression seal and spray pattern.