Coils

An ignition coil is a transformer with two windings. Current flows through the primary coil, building a magnetic field. When that field collapses, the secondary coil steps the voltage up to as much as 50,000 volts. That high voltage travels through the distributor cap, coil wire, and spark plug wire to the spark plug, where it jumps the gap and ignites the air-fuel mixture. A stronger coil delivers more energy and a more consistent spark.

A single ignition coil feeds all cylinders through a distributor and one high-voltage coil wire. A coil-on-plug system puts an individual coil at each cylinder with no distributor. The round oil-filled coils on this page are built for distributor-based ignition systems. If you're running an LS engine, FiTech also offers LS3 coil packs for coil-on-plug setups.

It depends on your ignition system. The oil-filled round coils do not include a ballast resistor. If your application uses a points ignition distributor, you'll need a low-ohm ballast resistor (typically around 0.9 ohm) installed on the positive wire. Late-model electronic ignition systems and FiTech ignitions do not require a ballast resistor.

The Go Spark Ignition Coil (90001) has matched impedance for the FiTech CDI box and up to 50,000 volts of output. Running a coil with the wrong primary winding resistance can reduce spark energy or damage the ignition control module. If you want a guaranteed match, the CDI + coil kit bundles both.

Common signs of a defective coil include a check engine light with a misfire code, rough idle, hard starting, and a drop in fuel economy. If the engine cranks fine on the starter motor but won't fire or runs rough, a weak coil is a likely culprit. Unburned fuel from a misfire can also damage the catalytic converter over time. Check the primary and secondary winding resistance against spec before replacing, and pair a new coil with new plugs. Contact tech support if you need help.