How to

How to test ignition coils

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A poorly performing ignition coil could lead to problems with vehicle performance and efficiency. Learn how to test an ignition coil with this Masters Of Motion video guide from our Delphi Technologies expert.

Ignition Vehicle Electronics & Engine Management How to Technicians 1 min read

How does the design of ignition coils differ?

The design of an ignition coil can range from 2 to 7 pins and everything in between. Also, they could be single coils or multiple, molded into a single housing.

Does the design of an ignition coil affect how you test it?

Yes. An ignition coil has two elements inside – the primary (the lower voltage) and the secondary (the higher voltage that ignites the spark plug). When testing the coil, you need to test the secondary voltage so it’s important to align the equipment up to that element.

For multiple coils molded into a single housing, you need to use a testing wand. This will pick up the back EMF during operation and send to the oscilloscope for you to review. This will help you identify which coil is causing the problem.

Do I need to test the primary side as well as the secondary?

Before you test the ignition coils, it’s a good idea to check that the primary 12 volt circuit is functioning properly. This is to confirm that the ignition coil has supply voltage and is working correctly.

Should the charge and burn times of the ignition coils be the same?

Not exactly, no. Small differences in the spark plugs will affect their charge and burn times, so expect there to be some variances. However, if one ignition coil was showing its burn time as extremely short or long compared to the others, then this could indicate a fault. The next step would then be to make sure that the spark plug was correct and is gapped correctly.

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