Although most of us seldom think about an ignition module until a tow truck arrives with a cranking, no-spark problem, the ignition module is still an important part of ignition system diagnostics and repair. Looking back into history, "solid-state" or "transistor ignition" systems made their first appearance on production vehicles during the 1960s. As emissions standards tightened during the 1970s, electronic ignition systems proved their worth because, unlike contact point distributors, they didn't need frequent adjustments and service. In addition, their solid-state electronics provided much higher firing voltages with much greater spark timing accuracy than did conventional point ignition systems.

IGNITION SYSTEM BASICS
Although thousands of different design variations in ignition modules now populate today's import ignition market, it's important to understand that all electronic ignition systems share the same basic functions. To produce a high-voltage spark at the spark plug, any ignition module must a) time the spark by sensing crankshaft position, b) saturate the primary windings of an ignition coil by turning the ignition system's primary circuit on, and c) collapse the resulting magnetic field in the ignition coil by turning off the primary circuit.

To better visualize ignition system operation, a soft iron core located internall...