How does a fuel injector work?
A fuel injector is nothing more than a high-speed valve for gasoline. An engine computer or controller is used to control the fuel injector. Contrary to popular belief, this is not done by sending power to the injector. Fuel injectors are normally fed power whenever the ignition key is on. The computer controls the negative, or ground side, of the circuit. When the computer provides the injector with a ground, the circuit is completed and current is allowed to flow through the injector. This energizes an electromagnetic coil inside the injector, which pulls a sealing mechanism (pintle, ball, or disc) away from its seat. This makes it possible for fuel to flow through the injector and into the engine. When the computer removes the electrical ground to the injector, the electromagnetic coil becomes demagnetized and a spring forces the pintle, ball, or disc shut to cut off fuel flow. Even at an engine speed of just 1000 RPM, this is done hundreds of times per minute.