Ignition Coil

All informations about this component of your engine

Functions of the Ignition Coil

The ignition coil must transform the relatively low 12 V on-board vehicle voltage to the high ignition voltage required and supply the energy stored in that voltage to the spark plug. The functional principle of the ignition coil is relatively simple. It has a primary winding (small number of turns) and a secondary winding (lots of turns). The turn ratio between the number of primary and secondary winding turns determines the level of the voltage generated at the output. When on-board voltage is connected to the primary winding of the ignition coil, a current flows through the primary winding, generating a magnetic field in the ignition coil. Interrupting the current flow in the primary winding takes away the magnetic field suddenly, simultaneously generating the high voltage required for ignition sparking in the secondary winding. How the high voltage generated by the ignition coil is transferred to the spark plug will vary depending on the ignition system, the vehicle generation and the vehicle model. In older vehicles, a mechanical ignition distributor distributes the high voltage to the spark plugs. The ignition distributor was replaced when fully electronic ignition with direct connection between ignition coil and spark plug was introduced.
Symptoms of a Faulty Ignition Coil

One of the most common symptoms of a faulty ignition coil is when the vehicle runs for a while and then the car's engine suddenly dies for no apparent reason. This occurs after the ignition coil or module gets too hot, and usually will correct itself after the engine module cools. In some cases, a bad ignition coil will result in the vehicle not starting it all. Or, it may have characteristics of a flooded carburetor, where the vehicle runs very poorly or jerks and stops erratically.
How to Diagnose a Faulty Ignition Coil ?

If your engine is backfiring, stalling or failing to start and you have noticed a significant decrease in fuel mileage, these could be signs that your ignition coil is failing. As with any automotive trouble, it is always best to confirm the source of the problem before replacing any parts. You can use a digital ohmmeter to test your vehicle's ignition coil at home. Purchase a replacement coil from a dealership or auto parts store if you find that yours is faulty.

1. Use a socket and ratchet to disconnect the negative battery cable. Place the cable securely away from the battery.

2. Pull the feed wire out of the coil. The feed wire is a large wire that typically connects to the top of the coil. Use a wrench to remove the bolts securing the remaining wiring to the coil. If there are no nuts securing the wires, release the locking tabs and pull the wires straight out of the connection.

3. Connect the red test lead of a digital ohmmeter to the primary side of the coiland the black test lead of the ohmmeter to the secondary side of the coil. The displayed reading on the ohmmeter should be between 0.7 and 1.7 ohms. You may have a faulty ignition coil if the readings displayed on your ohmmeter are not within this range.

4. Connect the red test lead of the ohmmeter to the coil's high-tension terminal and connect the black test lead to the coil's negative connection. The reading displayed on the ohmmeter should fall between 7,500 and 10,500 ohms. Your coil may be failing if the reading is not within this range.

5. Reposition the feed wire back onto the high-tension terminal. Secure the remaining terminal wires on the coil. Reattach the battery cable to the negative terminal and tighten it securely with a socket and ratchet.

How to clean the ignition coil ?


Decarbonization is recommended every year or 10,000 miles.

Preventive engine cleaning enables you to restore engine parts rather than replacing them, thereby saving vehicle owners on costly parts, such as a new turbocharger (1.350€ - 3.100€), catalytic converter (600€ - 2.000€), DPF (600€ - 2.000€) or EGR valve (370€ - 500€).

These problems result mainly from poor combustion, which stifles the engine.

So before replacing your engine parts, try Carbon Cleaning. A dirty engine as the result of carbon deposits is the new threat to vehicle performance.

Make your online diagnosis
How to replace an Ignition Coil ?

1. Open the hood and locate the vehicle's ignition coil.

2. Connect the spark tester to the ignition coil output.

3. Crank the engine to verify a spark.

4. Follow a wiring diagram to determine if the coil is power or ground side controlled. If controlled by ground, connect the test light clip to the power side of battery and touch the test light to the negative side of the coil.

5. Crank the engine and look for the test light bulb to flash.

6. Disconnect the negative battery terminal and electrical connections to the coil.

7. Remove the coil wire to cap.

8. Remove the ignition coil from vehicle and install a new ignition coil.

9. Reverse the removal procedures for installation.

10. Start the vehicle and perform a road test to verify the ignition coil is working properly.
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