The main function of the ignition system is to create a spark at the correct time. Two circuits accomplish this task, a primary and a secondary. The primary circuit converts a low voltage signal into a high voltage output. The secondary circuit distributes the high voltage to each cylinder at just the right time during the compression stroke of the engine

Read on to learn more about our ignition system components. You can also shop ignition online, or call or come in to one of our locations and a parts professional will be happy to assist you.

Primary Circuit

The primary circuit begins at the battery and ends at the ignition coil. As power flows trough the primary winding, a magnetic field builds up just like in an electromagnet. When the power flow is abruptly turned off, the magnetic field collapses. This induces a pulse of high voltage in the secondary winding of the coil.

Points and Condenser

The points control the primary circuit flow and the condenser keeps the points from arching. NAPA breaker points use 99% pure tungsten contacts to prevent burning.

Secondary Circuit

The secondary circuit consists of the ignition coil secondary winding, the distributor cap, rotor, spark plug wires, and spark plugs.

Distributor Cap and Rotor

The distributor cap and rotor transfer high energy from the coil to the spark plugs. These parts are made from an insulating plastic to contain the high voltage. NAPA’s distributor caps have many features designed for safety and efficiency. A few of these features are multiple ribs which prevent flash over, a vent to reduce ozone buildup, glass fiber reinforced thermosetting polyester construction, and brass contacts and terminals which don’t oxidize over time. NAPA’s rotors are made from dielectric mica/glass filled polyester plastics.

Ignition Coils

There are four main types of ignition coils: oil filled coils, laminated E-core (or HEI coil), distributor-less ignition system (DIS) coil pack, and coil on plug/coil near plug (COP/CNP)

COP means there is a direct connection to the spark plug. This can mean a faster crank to run time, better fuel economy, cleaner combustion, and reduced radio frequency interference.

Sensors and Controls

Ignition Control Modules

Ignition control modules are solid state devices that control primary circuit switching and control timing during start up. Breaker points performed this function in conventional systems.

Pick-Ups and Sensors

Pick-ups are devices that send timing signals to ignition control modules or the vehicles pcm (primary computer). Three basic types of pick-ups include magnetic, hall effect, and photo-optical

Crank and cam sensors work like a distributor mounted pick-ups, sending a signal to the ignition control module. The sensors are usually mounted in the engine block or bell housing. 

Spark Plugs

Spark plug electrode construction represents a huge area of research with many available options. You may find spark plugs with electrodes made from nickel, copper, platinum, iridium, or tungsten, or, more than likely, an alloy of 2 or more of these metals. The metal makes a difference in the service life of the spark plug, the combustion chamber temperatures, and even the NOx Output. 

The IMEP, or indicated mean effective pressure, is a measurement or the average work produced during one engine cycle. We rely on IMEP to determine a spark plugs ability to conduct heat away from the combustion chamber and to calculate the heat range. It is very important that you choose a spark plug with the appropriate heat range for your vehicle. 

Ignition system performance relies on the compatibility between various components in terms of fit, form, and function. We recommend you talk with a parts professional to get the correct part for your vehicle.


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