What a fuel injector actually does

The fuel pump provides the supply. An injector controls when fuel enters the engine and helps break it into a spray. In an electronically controlled gasoline system, the engine computer commands the injector rather than leaving the dose to a carburetor’s airflow-driven circuits.

An opening command is only part of the dose

An electrical command opens the valve for an injection event. Pulse width is the commanded time, but delivered fuel also depends on injector flow characteristics, pressure difference and the valve’s opening and closing behavior. Longer duration generally delivers more fuel when those other conditions stay comparable.

Bosch’s port-injection explanation discusses control of actual valve-opening duration and the effect of pressure on the fuel dose. Milliseconds alone are not a universal quantity of fuel.

Where the spray goes

Port injection sprays upstream of the inlet valve. Air and fuel pass into the cylinder during the intake event. Direct injection places the injector tip at the combustion chamber, where it meters and atomizes fuel at much higher pressure. Bosch describes that rail-to-chamber interface for its gasoline direct injectors.

Location changes the mixture-formation problem, pressure requirements and injector construction. It does not turn the injector into the pump. Some systems combine port and direct injection; the two terms describe where the respective injectors deliver fuel.

A mixture or misfire complaint cannot identify an injector from its name alone. Supply pressure, electrical control, airflow and ignition are part of the same engine system. The pictured connector and seal identify features to understand, not a reason to bypass that diagnosis.