Ignition System: Description and Operation

The ignition timing advance and spark duration characteristics are controlled by the Multi-Point Fuel Injection (MPI) controller. This engine uses a Direct Ignition System. It employes a multiple power transistor pack and ignition coil pack. There is no distributor, cap, or rotor.
When the ignition key is turned on, battery voltage is supplied to the positive side of the primary and secondary windings of the ignition coils through the ignition coil relay. As the engine begins to turn, the crank angle sensor determines the engine rpm and camshaft position and sends this information to the MPI controller. Based upon a determination made by several sensors as to the proper ignition timing requirements, the MPI controller then supplies a pulsed ground signal to the base of the power transistors. The power transistors cut the voltage to the primary windings in the ignition coils. This causes the magnetic field surrounding the primary windings to collapse and a voltage surge is created in the secondary windings of the ignition coil. High voltage (approximately 20,000 volts) flows out of the coils and into the spark plug. The voltage then jumps the gap at the spark plug electrode completing the path to ground, igniting the fuel mixture.