How to Test an Ignition Coil Pack

Written by eric w. thompson
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How to Test an Ignition Coil Pack
The ignition coil pack emits a magnetic current to ignite the spark plugs. (Jupiterimages/ Images)

The ignition coil pack in your vehicle is made up of two spools of copper wiring, which initiate the firing of the spark plugs. When you start the vehicle, a magnetic current spins an electrical contact, which in turn emits an electrical signal through a wire to ignite the plug. If the magnetic current weakens, the ignition coil will malfunction. Testing the ignition coil is fairly straightforward, so you can perform this procedure yourself and save a good deal of money.

Skill level:

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Things you need

  • Jack
  • Jack stands
  • Volt ohmmeter

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  1. 1

    Open the bonnet and trace the spark plug wires from the spark plugs to the ignition coil pack. The spark plugs are usually located on top of the engine, near the middle. The ignition coil pack is a domed metal cylinder with an extended tower, and is often located on one side of the engine.

  2. 2

    Pull the electrical connector from the ignition coil by hand, then unbolt the coil pack using a ratchet and socket.

  3. 3

    Turn the volt ohmmeter on and set it to the range of 2000 ohms. Place one meter lead to a spark plug terminal on one coil and the other lead to another spark plug terminal on the same coil. A reading between 5000 to 15,000 ohms indicates that the coil's secondary windings are in the proper resistance range. Anything below or above that range means the secondary windings need to be replaced. The secondary windings make up the inner part of the coil.

  4. 4

    Adjust the meter to the range of 10 ohms. Place one meter lead on terminal B+ of the coil pack electrical receptical and the other lead to the B+ prong of the electrical connector. The B+ terminal is the centre prong on the electrical connector. If the reading is above 0.3 ohms or above 1 ohm, the primary windings will need to be replaced. The primary windings make up the outer part of the coil.

  5. 5

    Repeat the previous testing procedure for the primary and secondary windings of each coil.

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