How to Troubleshoot an Ignition Coil

by Tara Kimball

The ignition coil generates the spark that feeds the spark plugs of the engine. An engine that does not receive the proper spark from the ignition coil will sputter, stall. Test the ignition coil before you replace it to confirm that it is the source of the problem. You can test the ignition coil yourself with a digital multimeter. You can find replacement coils at an automotive dealership or auto parts store if you determine that you need to replace it.


Remove the cable from the negative terminal on the battery. Put the cable in an area where it is out of reach of the terminal.


Raise the hood of your car and find the ignition coil in the engine compartment. Look for a cylinder shape or a flat, square-shaped part with a large wire feeding into it.


Pull the large feed wire off the ignition coil. It will pull straight off. Disconnect the other wiring from the coil by releasing the locking tab and pulling them straight off the connectors. If the wiring is secured with a nut, use a socket and ratchet or a wrench to remove the nut.


Use a multimeter set to ohms and test the coil’s primary and secondary sides. Connect the red lead from the meter onto one connector and the black lead of the meter onto the other. Note the resistance displayed from the two connectors. The reading should range from .7 to 1.7 ohms. A result outside of this range may indicate a faulty coil.


Connect a test lead to the high-tension terminal and connect the other lead to the coil’s negative connection. The reading on this test should be anywhere from 7,500 to 10,500 ohms. A result outside this range may mean your coil is failing.


Reconnect the wiring to the coil and connect the coil wire to the high-tension terminal. Replace the negative battery cable to the terminal.

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About the Author

Tara Kimball is a former accounting professional with more than 10 years of experience in corporate finance and small business accounting. She has also worked in desktop support and network management. Her articles have appeared in various online publications.

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