What does a fuel injector do?

A fuel injector sprays a precise, metered amount of fuel into the engine — into the intake port or directly into the cylinder — where it mixes with air for combustion. Modern engines use electronic fuel injection (EFI) controlled by the engine computer, which has largely replaced the older carburetor. Precise injection improves fuel efficiency, power, and emissions control. The injector's job is delivering the right amount of fuel at the right time. Understanding fuel injection versus the older carburetor system is common Auto Information content on the fuel-system topic.