How fuel injector is operated?

A fuel injector is pretty much like an electric solenoid. The injector is therefore an electrical and mechanical component. It opens and closes a plunger which is pulsed in the injector by the on board computer. The computer uses all the other sensors on the vehicle to calculate how long or how many pulses needed to keep the fuel injector open. Fuel is driven to the injector or injectors by an electric pump which also is regulated by pressure. The injector is closed before compression of the engine or is opened on the down stroke of the cycle. In other Words; when the injector has electricity going to it, then it opens. Without electricity it naturally closes.