Follow crank/cam synchronization, injector command, and the difference between electrical pulse width and delivered fuel.
Relate a four-stroke 720° cycle to sequential injector commands; predict how RPM changes the time available per cycle; distinguish injector electrical command from fuel delivery; and use a simulated scope and scan-tool readings to investigate faults.
Illustrative four-cylinder, four-stroke, port-injection teaching model. Injection is shown near each cylinder's intake event; real injection timing, strategies, injector drivers, and waveform shapes vary. Do not use these values as OEM specifications.
Illustrative firing order: 1–3–4–2. Injection markers are training references, not an OEM calibration.
A colored bar indicates an injector's electrical ON interval; the vertical cursor is crank position. Batch mode groups cylinder commands for comparison.
Simplified low-side driver: near battery voltage when OFF, near ground when ON. A real inductive injector can produce a flyback spike when switched OFF; this diagram omits its exact shape and amplitude. An open circuit can have a misleading voltage trace: verify current and circuit integrity.