Ignition Circuits
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Ignition Circuits

Primary Ignition Circuit
The primary ignition circuit operates on battery voltage with the ignition switch on and the engine stopped, or changing system voltage with the engine running.

Ignition Dwell Time (Saturation)
The ignition dwell time is the length of time that the primary circuit is turned on prior to each cylinder firing. The internal module circuit determines the actual time that the primary circuit is closed (dwell time). Primary circuit dwell time is important because the primary current must flow long enough to allow the magnetic field to build up in the coil. The dwell time is not adjustable because the module determines when the circuit is closed.

Secondary Coil Voltage
The normal required secondary coil voltage of 10,000 volts is determined by the spark plug gap. Many coils have a maximum secondary voltage in excess of 30,000 volts. The difference between the normal required secondary coil voltage and the maximum secondary coil voltage is referred to as secondary reserve voltage. This reserve voltage is necessary to compensate for high cylinder pressures at wide throttle openings and the secondary resistance increases as the plug gaps become wider. Miles or kilometers of operation gradually erode the plug electrodes and create a higher secondary required voltage. Increased cylinder pressures between the spark plug electrodes at wide throttle openings also increase the secondary required voltage. The maximum secondary coil voltage must always exceed the normal required secondary coil voltage, or misfiring will occur.

NOTE: The content contained in this section was compiled from information provided by professional ASE certified technicians, aftermarket and OEM sources.



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