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What are the Parts of an Ignition System?

By J.Gunsch
Updated May 23, 2024
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The ignition system in your car is like a large circuit board that distributes energy throughout the automobile to get it going and keep it running. The efficiency of this system not only makes your vehicle go but also influences the engine’s performance which translates into better fuel efficiency and less pollution from emissions.

There are two parts to an ignition system. The first one is called the primary side and the second is the secondary side. The primary side consists of the distributor and the electronic control module and the secondary consists of spark plugs and wires, an ignition coil, rotor and in some systems the distributor. The ignition system relies on the vehicles battery to provide a spark which sets the system in motion and starts the vehicle.

  • Ignition Key: The key is the first and most familiar part of an ignition system. When the key is turned it releases low voltage electricity from the primary circuit of the ignition system. This electricity then goes to the ignition coil.
  • Ignition system coil: this is an electromagnet as well as an inductor that transforms high voltages from the vehicles battery. The coil is connected to the distributor.
  • Spark Plugs: The spark plugs and spark wires force electricity to the engine creating a voltage of between 40,000 and 100,000 volts. Although they are simple and fairly small parts, when the spark plugs or wires get worn out, the vehicle will not run. This is why good vehicle care involves getting a regular tune-up.
  • Distributor: The distributor in an ignition system itself has two parts; the rotor and the distributor cap. Like the name implies, this part distributes electricity from the coil to the spark plugs and wires and the cylinders of the vehicle’s engine. The number of cylinders depends upon the vehicle but is commonly either four or five cylinders. Like spark plugs and wires the distributor cap and rotor become worn out and need to be replaced periodically.

Many newer vehicles have ignition systems that do not have a distributor which are appropriately called a distributor-less system. The work of the distributor is done directly through the use of modified spark plugs. This type of system also does not contain spark plug wires. These vehicles are more environmentally friendly and fuel efficient as well as reducing the need for frequent tune-ups.

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Discussion Comments
By kentuckycat — On Jul 04, 2011

@Izzy78 - Thank you for the great information! I did a few online searches, and poked around my engine a little bit. I have a six cylinder engine, and it looks like the spark plugs are on the bottom. Since that is the case, I think I'll just let my mechanic handle it. I'm not sure that I would have the right tools, anyway, so I probably wouldn't have saved much in the end.

For anyone who is more mechanically inclined, the process seems fairly simple. I guess I'll keep limiting my mechanic skills to changing my oil and filling up the washer fluid.

By TreeMan — On Jul 04, 2011

This article mentions 5 cylinder engines, but I have never heard of that before. Every engine I have seen is either 4, 6, or 8 cylinders. Engines are typically set up with two rows of cylinders so that the car stays balanced.

Are the 5 cylinders in a line? Also, what kinds of cars use them, and what kind of performance do those cars have compared to 4 and 6 cylinder engines?

By Izzy78 — On Jul 03, 2011

@kentuckycat - I have actually installed my own spark plugs before. I didn't find it to be very difficult, but I think a lot it would depend on your engine and your confidence. Replacing them is simple as long as you can reach them. I have a 4 cylinder car, and the spark plugs are located on top of the engine within easy reach.

I know on larger 6 and 8 cylinder engines, the spark plugs are often located along the sides at the bottom of the engine, and reaching them can be tough. I would recommend doing an online search for changing spark plugs. You should be able to find some detailed guides. If you have the right tools, changing the spark plugs yourself can save around $75 dollars depending on your mechanic.

By kentuckycat — On Jul 03, 2011

Has anyone here ever tried to replace their own spark plugs? I know I have heard of people doing it, and I thought it might be able to save me some money in the long run. Even if it is easy to do, should I spend my time doing it myself, or just let my mechanic do it during a tune up? I just don't want to cause any ignition problems on my car because I got overzealous.

Another thought I had during this article was how the ignition system on a diesel engine works. Since there aren't any spark plugs, is there still a distributor and coil? If so, what are their functions?

By JimmyT — On Jul 02, 2011

I never realized how much was involved in the ignition system. I've always just considered the ignition system to stop at the place where I insert the key.

I wasn't aware that there were "distributor-less" systems, either. Do these somehow use a special computer system to control the spark plugs? If not, how are they controlled? Also, how do they make the car more fuel efficient and better for the environment?

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