Ignition System: Description and Operation

The ignition system consists of a Multi-Point Injection (MPI) controller and its sensors, power transistor, ignition coil, and distributor that sends crank position information from the crank angle sensor and piston location information from the Top Dead Center (TDC) sensor to the MPI controller as well as distributing coil secondary output. The MPI controller controls the entire ignition and fuel injection system. It gives the capability of igniting the fuel mixture according to different engine conditions during engine operation by delivering a variable electronic spark advance curve. The MPI controller has a built in microprocessor that continually receives input from the engine monitoring sensors. The computer then electronically advances or retards the ignition timing to provide good driveability during operation. The amount of electronic spark advance provided by the MPI controller is determined by three input factors, coolant temperature, engine rpm, and manifold vacuum.