A fuel delivery system whereby gasoline is pumped to one or more fuel injectors under high pressure: When a fuel injection takes place at the appropriate times, the fuel injectors, which are valves, open to allow fuel to be sprayed or atomized into a throttle bore or into the intake manifold ports.

The fuel injectors are usually solenoid operated valves under the control of the vehicle's on-board computer resulting in electronic fuel injection.

The fuel efficiency of fuel injection systems is less temperature-dependent than carburetor systems. Diesel engines always use injectors.