YESTERDAY’S IGNITION SYSTEMS
As a young auto mechanic in the 1970s, I frequently heard the phrase, “My car
needs a tune-up.” The common complaint? The customer felt the engine was
running poorly, usually meaning the ignition system needed to be refurbished. In
the old days, ignition systems consisted of a set of electrical breaker points that
were driven by the distributor (the part that governed the firing of the spark from
the ignition coil), a condenser (the part that stored electricity when the points
were open to prevent misfiring), a mechanical spark distributor, distributor cap
and rotor, sparkplug wires, and sparkplugs. This system had many bugs that
demanded constant attention.
The way the system worked was really quite simple. The distributor was
mechanically driven (spun) off the camshaft or some other gear-driven engine
part. This spinning action caused the points to open and to close, making and
breaking the electrical circuit between the ignition coil and the distributor. This
making and breaking of electrical flow caused voltage to buildup within the coil
and a high-intensity spark was dispersed through the distributor cap to the rotor
at precisely the correct time. The rotor delivered the spark to each tower on the
distributor cap. The spark traveled through a sparkplug wire that was connected
to the tower and eventually arrived at the spark plug. At this point it jumped an
air gap and ignited the compressed, highly volatile air-fuel mixture in the
combustion chamber. This process created the energy needed for the downward
power stroke to power the engine.
This design is simple in theory. But, as with any mechanical or electrical
system, there’s always a weak link that causes failure or poor performance. In
this case, there were several weak links: the electrical points, condenser,
distributor cap, and rotor. Points wore out, condensers grounded internally, and
distributor caps and rotors developed cracks and dirty contacts, which resulted in
misfire, backfiring, stalling, hesitation, and a myriad of other complications. The
insulation on sparkplug wires broke down frequently from extreme changes in
temperature that caused voltage leakage. This leakage caused cross firing and
“breakdown under load.” Under heavy load conditions, such as hauling a heavy
trailer, the engine would miss, hesitate, and backfire. Sometimes this even
happened when tooling around town, up and down hills, with a full passenger
load. Yes, early ignition systems certainly had their idiosyncrasies.
The mid-1970s brought electronic systems with their solid-state design.
Characteristically, these systems offered better performance overall. However,
they had their own special set of problems. They were affected by engine heat