How to test a pickup coil

By: Leon Rhodes

To troubleshoot pesky engine starting issues it's often a good idea to test its ignition pickup coils, sometimes called spark coils. Typical ignition pickup coils have two coils of wire, called primary and secondary coils, tucked inside their casing. Primary pickup coils draw power from the vehicle battery and secondary pickup coils send it to the engine's spark plugs.

multi-meter used to Test Pickup Coils

Each coil operates within a manufacturer specified resistance range. You can test the total resistance of your pickup coil with a simple multi-meter tool, here's how:

  1. Set your multi-meter to read resistance, also called ohms, typically labeled with the Ω symbol
  2. Attach the negative (black) lead from your multi-meter to the negative outer terminal of the ignition coil
  3. Connect the positive (red) lead from your multi-meter to the positive outer terminal of the ignition coil
  4. If the resistance reading is within the range specified by the manufacturer the primary ignition coil is good
  5. Next, move the negative (black) lead from your multi-meter to the negative center terminal of the ignition coil

If the multi-meter's secondary resistance reading is also within the manufacturer specified range the pickup coil is good

What are failing ignition coil symptoms?

Failing ignition coils cause a wide range of engine performance issues and can lead to alternator damage and check engine lights. They also may cause engine misfires, rough idling, a decrease in performance, poor fuel economy and difficulty starting the engine.

Can you drive with a bad ignition coil?

While possible it is not recommended to drive with a bad ignition coil because it can lead to engine damage. Typically, the owner suspecting a faulty ignition coil should diagnose and, if needed, replace the coil as soon as possible. Systems damage occurs while driving with a faulty coil in as little as a week.

How do ignition coils go bad prematurely?

Premature coil failure is common when spark plug wires become damaged. Additionally, overheating conditions, unusually high battery currents and excessive engine vibration can all cause ignition coil damage.

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