THEORY OF OPERATION - CONTINUED
ENGINE - CONTINUED
Fuel Injection Timing and Delivery.
ECM controls injected fuel amount by varying signals to fuel injectors. EFIs will inject fuel ONLY if fuel
injector solenoid is energized. ECM sends a 90V signal to solenoid to energize it. By controlling 90V sig-
nal timing, ECM controls injection timing. By controlling 90V signal duration, ECM controls injected fuel
Injection timing is determined by engine rpm and other engine data. ECM senses top center position of
cylinder No. 1 from signal provided by engine speed sensor. ECM decides when injection should occur
relative to top center position and provides signal to fuel injector at desired time.