Fuel Injector(s)
Samurai, Sidekick (8-valve) and Swift SOHC use Throttle Body Injection (TBI), which incorporates a single fuel injector in the throttle body unit. Sidekick (16-valve) and Swift DOHC use Multipoint Fuel Injection (MPI), which incorporates 4 fuel injectors mounted in a fuel rail assembly. MPI system injects fuel/air mixture directly into cylinder head intake ports.
On all models, when the solenoid coil of injector is energized by ECM, coil becomes an electromagnet. See Fig 1 and Fig 2 . This lifts injector plunger, allowing fuel under pressure to be injected into intake manifold (Samurai, Sidekick TBI and Swift SOHC) or cylinder head (Sidekick MPI and Swift DOHC). Since fuel pressure is relatively constant, air/fuel mixtures are controlled solely 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 RPM signals received from either distributor P/M generator (Swift DOHC) or ignition coil (Samurai, Sidekick and Swift SOHC). On Swift SOHC, 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.