What a fuel injector actually does
A fuel injector is an electrically timed valve that sprays metered fuel into a port or the cylinder. Pulse width is the dose. It is not the fuel pump and not a carburetor.
People treat this like the fuel pump. Or like a leftover carburetor still mixing in the hole. It is neither. A fuel injector is an electrically timed valve. The box opens a pintle. Fuel sprays.
The pump only fills the rail. Rail pressure sits upstream. What the PCM meters is pulse width — how many milliseconds that pintle stays off its seat. Longer pulse, more fuel. Shorter pulse, less. The spray lands in the intake port, or it lands in the cylinder. Port or direct. Both are still injectors.
Do not start at the throttle body because the mix is off. That plate meters air. Do not start at the MAF. That film counts air. A clogged pintle, a leaking O-ring, a dead coil in the connector — those are this part. The bag on the seat is just the inlet end of the same valve.
