Ignition Coils & Parts

The ignition coil transforms the 12 volts supplied by the vehicle battery and charging system into the 15,000 – 40,000 volts needed to jump the gap between the spark plug electrodes and ignite the air/fuel mixture in the cylinders. It’s the link between the primary and secondary circuits in the ignition system. The low voltage, primary circuit includes the battery and charging system, ignition switch, triggering device, and the coil’s primary windings, while the secondary circuit consists of the secondary coil windings, the high tension lead and distributor cap and rotor on distributor ignition systems, and the spark plug wires and spark plugs. If you’re in need of a replacement ignition coil, we have coils and related components for all types of ignition systems including breaker point and electronic distributor ignitions, DIS (Distributorless Ignition Systems), and COP (Coil On Plug) and CNP (Coil Near Plug) systems.

A typical ignition coil contains two coils of insulated copper wire, the primary and secondary, wrapped around an iron core, inside a plastic, epoxy or polymer housing. Several hundred windings of the thicker, approximately 0.030” (0.75mm) diameter primary wire surround the core. The thinner, approximately 0.025” (0.63mm) diameter secondary wire surrounds the iron core with many thousands of windings, within the primary windings. The primary windings are connected to battery voltage and the triggering device through terminals on the coil housing. The secondary winding is connected to the coil high tension tower. When the ignition switch is on, current flowing through the primary windings creates a magnetic field. When current flow is interrupted by the triggering device – breaker points, pickup coil and trigger wheel, or ECU (Engine Control Unit), depending on ignition system – the collapsing magnetic field produces an electric current in the secondary windings, which is stepped up to the 15,000 – 40,000 volts that exits the high tension tower.

In a breaker point or electronic distributor ignition system, voltage from a single ignition coil travels from the coil through a high tension lead to the center tower of the distributor cap. A rotor, mounted on the distributor shaft and connected to the distributor cap coil tower, distributes the voltage to the individual cylinder towers at the perimeter of the cap as the distributor shaft rotates. The spark plug wires attached to the distributor cap cylinder towers deliver the voltage to the spark plug in each cylinder. DIS systems have two or more coils in a coil pack, with each coil supplying voltage to the spark plugs in two cylinders on every revolution of the crankshaft, with one spark plug firing in the cylinder on the compression stroke and the other in the opposite cylinder in the firing order that is on the exhaust stroke. Because the spark in the cylinder on the exhaust stroke has no effect on engine operation, this is commonly called a “waste spark” ignition system. In COP ignition systems, also called direct ignition, an ignition coil is directly attached to each spark plug. CNP systems also feature a coil for each cylinder, but the coils are connected to the plugs with short spark plug wires.

An ignition coil can fail suddenly or deteriorate gradually. On a vehicle with a single ignition coil, sudden failure will result in a no-start, while complete coil failure on DIS, COP, and CNP systems will be revealed as a dead cylinder and rough idle, poor performance and fuel economy, usually accompanied by a CHECK ENGINE light illuminated on the dash. Age and continual exposure to heat and vibration can cause cracks, corrosion and coil failure but so can excessive resistance in the spark plug wires and larger than normal electrode gaps in worn spark plugs, both of which force the coil to work harder trying to develop the voltage to overcome these adverse conditions. If a malfunction indicator light is illuminated or a misfire is suspected, check for DTCs (Diagnostic Trouble Codes) with a scan tool. The coil resistance can be checked with a DVOM (Digital Volt Ohm Meter) and compared with specifications, and a faulty coil can also be revealed by viewing the voltage pattern on a diagnostic scope.

No matter what vehicle you’re working on or what kind of ignition system it has, we have the replacement ignition coils and related components needed to restore proper performance, reliability and fuel economy. We offer ignition coils and components that are manufactured to original equipment specifications, so when repairs are completed you can count on the performance your vehicle was designed to deliver. In addition to an extensive selection of distributor ignition system coils, DIS coil packs, and direct ignition, COP and CNP ignition coils, we also offer related components that you may need to make an effective and complete repair including ballast resistors, coil boots, coil bolts, coil connectors, coil covers and cover gaskets, coil housings, coil mounting brackets and mounting gaskets, coil seals and coil ground straps. We also carry performance ignition coils that provide more powerful output than standard ones, ensuring more efficient combustion. And with reputable brands that we carry, including but not limited to Denso, Bosch, TRQ, Delphi, and ACDelco, you know you’re getting high-quality products.