This fuel injector delivers a metered quantity of high-pressure fuel into the combustion chamber of the host engine. It is mounted in the cylinder head and receives fuel from the high-pressure common rail or injection pump. The injector opens and closes in response to an electronic or mechanical signal, controlling the start of injection, injection duration, and fuel atomization. A worn or fouled injector causes uneven engine running, reduced power, increased exhaust smoke, and higher fuel consumption. The manufacturer machines the injector nozzle and internal valve to the original flow-rate specification, which the engine control unit relies on for balanced cylinder-to-cylinder fueling. When replacing, use new sealing washers and tighten the injector clamp to the specified torque.