The ignition coil is one of the main components of a car’s ignition system. Without it, a car can’t run.
As a vital component of any vehicle, it is important to know the role played by a car’s ignition coil and the tell-tale signs that it is time to replace it.
Read on to find out how a car’s ignition coil works.
What is an ignition coil?
Ignition coils transform battery voltage, that is, the volts, which vary between 12 and 14V, to a higher voltage, allowing engine combustion to be sparked by the spark plug.
If a car’s ignition coil is faulty, the fuel cannot be burned correctly. As a consequence, many problems may arise in your car.
What is the purpose of an ignition coil?
An ignition coil transforms battery voltage to the spark plugs, producing the sparks that allow combustion to take place and, consequently, the car engine to run.
Although the ignition coils of some vehicles are still connected to the spark plugs via wires, this isn’t the case for many cars, therefore avoiding a range of problems.
Ignition coils are required to increase ignition voltage. But why should the ignition voltage be increased?
How does an ignition coil work?
Getting a spark plug to fire requires a car’s battery voltage to be increased thousands of times. If the voltage is 12V, for example, the spark plug electrode is unable to produce a flame.
Similarly to transformer enhancers, ignition coils use magnetic induction to increase input voltage. As such, there are actually two coils: a primary and a secondary one.
The secondary coil is located inside the primary coil, which is inside the ignition coil.
How does ignition coil induction take place?
Contrary to popular belief, induction does not occur when a current passes through the ignition coil. In fact, it takes place when the current is cut off.
In short, the primary coil will emit a magnetic field around itself. When the electric current is cut off, this magnetic field quickly retreats back into the coil before disappearing. It is this rapid and simultaneous movement that induces the secondary coil, which produces more substantial results.
As a result, the secondary voltage increases from 12V to about 25KVA.
What is the role of an ignition coil’s iron core?
The iron core in an ignition coil pulls the primary coil’s magnetic field in, ensuring that the movement is focused quickly. This happens because iron is a good conductor able to maximise the coil’s induction properties.
What types of ignition coil are there?
Different ignition coils are available depending on the car and brand. These include:
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Distributor ignition coils
Distributor ignition coils: the high voltage impulse generated by the coil passes through an ignition cable to a mechanical ignition distributor.
This, in turn, distributes the thrust to the corresponding ignition cable, producing tension in the cylinder. It is very commonly found in older vehicles.
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Block ignition coils
Block ignition coils: this component is made up of several ignition coils that power the spark plugs by means of a high-voltage pulse via the respective individual outputs and ignition cables. This type of ignition coil encompasses both single- and twin-spark models.
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Outlet coils for spark plugs
Outlet coils for spark plugs: connecting directly to the spark plug, these coils have no need for ignition cables. The high voltage impulse is therefore generated directly to the spark plug, avoiding any voltage loss through the cable. This type also produces more space within the engine.
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Rails
Rails: composed of several ignition coils that combine to form a compact component; all ignition components are connected to the spark plugs in a single step.
What are the symptoms of a damaged ignition coil?
A damaged ignition coil will produce symptoms such as:
- A strong burning smell;
- Engine vibration when idling;
- Increased fuel consumption;
- “Check Engine” light on the dashboard;
- Heavy engine start, which stagnates when driving;
- Engine running unsteadily, especially in cold weather;
- Black smoke and petrol smell released through the exhaust pipe;
- The engine power drops significantly after pressing the accelerator.
Although these are signs that the coil may be broken, these symptoms may also indicate the breakdown of other components, such as high-voltage cables.
In such cases, you’ll want to look at the entire ignition system.
How can you test your ignition coil?
Before you can test your ignition coil, you’ll need to use a basic set of hand tools to remove the coil, as well as a digital multimeter.
Once it has been removed, you can follow the following steps:
- Find out the specifications of your coil, that is, the correct resistance reading that should be showing for your vehicle’s ignition coils (refer to your owner’s manual);
- Locate the coil (or coils). Ignition coils are generally located in the engine, screwed to the spark plugs or installed somewhere on top of the engine. If necessary, remove the plastic covers;
- Disconnect the power cord;
- Test the primary circuit by connecting the multimeter’s positive and negative wires to the corresponding coil terminals:
- Test the ignition coil’s secondary circuit by connecting the multimeter to the positive terminal and output terminal, which goes through to the spark plug;
- Repeat the procedure as needed;
- Once you’ve tested everything, reinstall the ignition coils.
If the coil shows a zero reading on the multimeter, it is a sign that it has internally shorted the primary windings and needs to be replaced.
How much does an ignition coil cost?
Prices of ignition coils can range between €20 and €200, depending on your vehicle and its specifications. However, an coil can cost far more in more “eccentric” cars.
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