How Ignitions Systems Work

The Basics Of A Car Engine

In order to understand how your vehicle's ignition system works we need to review the basics of internal combustion.

Basically, a car engine is like a large pump. Air and gas are being pumped in and exhaust is being pumped out. There is a by-product of excess energy that is being sent to the wheels and exhaust (which exits through the tailpipe). Your car's engine combines the air and the fuel, and adds a spark. The spark ignites the air and fuel mixture to cause an explosion. This is what we refer to as ignition.

The ignition system is a group of components that work in tandem to create the ignition. The ignition system contains an ignition coil, a distributor, a distributor cap, a rotor, plug wires and spark plugs. Older ignition systems use what is called a "points-and-condenser system" in the distributor. Current ignition systems like the one your car most likely contains uses an ECU. An ECU or an engine control unit controls the spark and ignition timing.

Well take this apart piece by piece so it all makes sense.

1. Ignition Coil

The ignition coil takes the weak battery power and turns it into a spark that is powerful enough to ignite your fuel's vapor. There are two coils of while in the ignition coil and they are right on top of each other called windings. The windings are differentiated as primary and secondary. The primary winding gathers the power to create a spark. The secondary winding sends it to the distributor.

There are three contacts on an ignition coil. If the ignition coil has an external plug, then the contacts are on the inside of the case. The large and obvious contact in the middle of the ignition coil is where the coil wire goes. The coil wire is the wire that links the ignition coil to the distributor cap. The second contact is a 12V wire that connects into a positive power source. The third contact sends information to the rest of the vehicle such as the tachometer.

2. The Distributor, Distributor Cap, and Rotor

As we mentioned above, your ignition coil links to the distributor via a coil wire. The distributor receives that powerful spark and sends it out to the spark plugs.

The distributor is a very precise spinner. It spins distributing the sparks to each of the spark plugs at the right time. The rotor, which is actually connected directly to the shaft of the distributor, is the mechanism that distributes the sparks. Since it's connected to the distributor, the rotor also spins and makes contact with a number of points that correspond to the number of cylinders your engine has. Then, it sends the spark through the point to the plug wire located on the other end. Modern distributors use electronic assistance that is able to alter the ignition's timing.

3. Spark Plugs & Wires

As we mentioned above, once the ignition coil creates the high-powered spark, the distributor and rotor takes that spark and spins it to the right outlet. However, we still need a way to transport that spark to the spark plug. This is done using spark plug wires.

The contact points on the distributor cap connect to a plug wire that takes the spark to the spark plugs. The spark plugs are screwed to the head of the cylinder.

The end of the spark plug is located at the top of the cylinder and that's where the action happens. Once the intake valve lets out just the right amount of fuel vapor and air in the cylinder, the spark plug creates a blue hot spark that ignites the mixture. This is what causes combustion. The ignition system does this thousands of times per minute.

4. The Ignition Module

Through an old system called "a points-and-condenser system", a distributor relied on many of its own mechanics to time the spark at just the right time. The ignition points were set to a specific gap, which created the proper amount of spark while the condenser did the regulating.

Nowadays, all of this is handled by computers. This computer is called an ignition module. If it malfunctions, all you can do is replace it since it cannot be repaired.

This should demystify this part of your car system a bit and that concludes Ignition System 101.