ignition rails are very strong and reliable, but can fail for various reasons. Heat and vibration can damage the windings and insulation of the coil, resulting in shorts or open circuits in the primary or secondary windings. But the number one killer of ignition coils is voltage overload caused by bad spark plugs or plug wires.

If the spark plug or plug wire has an open circuit or excessive resistance, the output voltage of the ignition coil may rise to the point of burning through the insulation inside the coil, causing a short circuit. If the output exceeds 35,000 volts, the insulation of many coils can be damaged. Once this happens, when the engine is under load, the output voltage of the coil may drop, causing the ignition to misfire, or the coil may stop outputting any voltage, preventing the engine from starting or running.

If the coil has battery voltage on its positive terminal and is being grounded or grounded through the ignition module or circuit without sparking, the coil is defective and needs to be replaced.

Tip: If the ignition module fails multiple times, it may be due to the ignition coil of the ignition coil core supplier being damaged. An internal arc or short circuit in the coil can overload and damage the circuitry inside the ignition module.