Electronic ignition module

A module, not a complete ignition unit

There are two ways to switch to electronic ignition. Replacethe entire ignition unit with an electronic model, which is straightforward but alters a visible part of the engine. Or install a module inside the original ignition unit, in place of the breaker and capacitor.

The module is the solution for meticulous restorations: nothing changes externally; the distributor remains the vehicle’s original unit with its markings and appearance, and only an attentive connoisseur looking under the bonnet might realise the modification has been made. It is also significantly cheaper than a complete distributor. On the other hand, it requires the distributor housing to be in good condition, as it is retained.

What the module eliminates

Inside a conventional ignition coil, the cam on the shaft mechanically spreads apart two contacts – the breaker – whilst a capacitor absorbs the arc to protect them. These two parts are subject to constant wear: the contacts become pitted, their spacing changes, and the ignition timing drifts between servicing intervals.

The module replaces this assembly with a contactless sensor – usually a Hall-effect or magnet-based sensor – and a power stage that controls the coil. Nothing rubs or wears down any more. The practical benefits are clear: no more gap adjustment, no more capacitor replacement, a more powerful spark at start-up, and, above all, an ignition point that remains exactly as set. What does not change, however, isthe centrifugal advance and the vacuum correction: these remain the same as those of the original distributor, with its weights and capsule, which must therefore be checked.

Check the distributor before ordering

A module only compensates for wear on the breaker. The rest of the distributor remains unchanged, along with any faults it may have.

• Shaft play: grasp the shaft and move it from side to side. Any noticeable play causes the ignition point to vary with every revolution, and no module will compensate for this.
• The centrifugal advance weights, which can seize up and block the advance at idle. They must return freely under their springs.
• The vacuum capsule, which can develop a leak: it must maintain the vacuum and move the distributor plate.
• The head and the pin, which can become worn and leak, particularly after years of weak ignition.

If the shaft has play or the body is worn, a complete electronic ignition system will be more suitable than a module.

Compatibility and tuning

• The ignition coil model into which the module is fitted: this is the decisive factor, and it is determined by the ignition coil body, not by the vehicle. A single vehicle model may have been fitted with several different ignition coils depending on the year and engine type.
• The presence of a vacuum line, which affects the available internal clearance and the module model.
• The on-board voltage, 6 V or 12 V, and the polarity, which is negative to earth on most set-ups but not all.
• The number of cylinders, which determines the number of firing points.

After installation, set the initial timing using a strobe light whilst the engine is warm: a module must not be fitted whilst the engine is at a standstill. Also check the coil, which must be compatible with the module; some require a minimum primary resistance, otherwise they may overheat.