Ignition System: Description and Operation

The ignition system consists of an ignition coil, ignition module, distributor, spark plugs, and spark plug wires. Ignition spark timing correction is achieved by an ignition module, Electronic Control Module (ECA), and crankshaft position sensor located in the distributor.

The crankshaft position and engine rpm are sensed by the crankshaft position sensor (CPS). The ECA then signals the ignition module telling it when to fire the coil. The module controls the current through the ignition coil primary winding. The module turns current on between firing points to build up a magnetic field around the coil windings. It then turns the current off on signal from the pulse generator and pickup coil. Once the current is turned off, the field collapses and a high voltage pulse of over 20,000 volts is induced in the coil secondary winding. The pulse is transmitted to the central terminal in the distributor cap, and through the rotor to the distributor cap terminal for the spark plug whose turn it is to fire. At the plug electrodes, in the combustion chamber, the high voltage arcs to ground, to ignite the compressed air/fuel charge in the cylinder.