Fuel Injector(s)
TBI (Throttle Body Injection), incorporates a single fuel injector in the throttle body unit.
When the solenoid coil of injector is energized by ECM, coil becomes an electromagnet. See Fig 1 . This lifts injector plunger, allowing fuel under pressure to be injected into intake manifold. Since fuel pressure is relatively constant, air/fuel mixtures are controlled by injector pulse width ("on" time). ECM determines proper pulse width based upon input signals received from various sensors and switches.
Timing of injector firing is determined by ECM based upon ignition signals from ignition coil. ECM also monitors ignition coil signal. Since ECM interprets coil signals as an indication of spark presence, fuel injector triggering will cease if ignition coil signal is lost.