How to Test an Ignition Coil?

[StSpencer]

Checking an ignition coil can be done by methods such as listening for sounds. Below are the methods to test an ignition coil: 1. Read fault codes: Use a computer diagnostic tool, insert it into the OBD port to read fault codes. If it shows intermittent misfire issues in a certain cylinder, it usually indicates a problem with that cylinder's ignition coil, which needs replacement. 2. Listen for sounds: During engine idle, pull out each ignition coil slightly and listen for crackling discharge sounds. If the sound is weak or absent, it suggests an issue with that cylinder's ignition coil. You can swap adjacent ignition coils for comparison. 3. Use a multimeter: Perform a diagnostic check on the ignition coil with a multimeter. For example, a four-wire ignition coil has power wire, ignition feedback wire, ignition signal wire, and ground wire. Use the multimeter to check the voltage of the ignition coil's feedback signal wire. When the engine is running, the normal voltage of the signal feedback wire should be around 5 volts. If it's below 5 volts, it indicates internal damage in the ignition coil.

[LeRyder]

My personal experience with testing ignition coils involves a three-step process. First, remove it for visual inspection to check for cracks or burn marks on the plastic housing, and pay attention to the aging condition of rubber components. Second, use a multimeter to measure resistance values by locating the primary and secondary test points. Primary resistance typically ranges between 0.5-2 ohms, while secondary resistance falls within 5000-20000 ohms. Last time when I measured infinite resistance on the secondary coil, I knew it had an internal break. Third, apply the substitution method by swapping the suspected ignition coil with a known good cylinder's coil. If the fault code follows the swapped coil, the diagnosis is basically confirmed. Always prioritize safety when DIY-ing—wear insulated gloves. I recommend keeping a repair manual handy to reference standard values for more reliable results.

[LunaMarie]

Testing ignition coils I have a professional approach: First, use a diagnostic scanner to read fault codes and confirm the general direction. Then remove the ignition coil and inspect for external damage. Measure the primary coil resistance with a multimeter—it should be less than 1 ohm. The secondary coil resistance typically ranges between 8,000 to 15,000 ohms, but refer to the vehicle manual for exact specifications. Cold-state testing is more accurate as resistance changes when the engine is hot. The swap test is the most practical method—exchange coils between two cylinders and observe if the misfire data shifts. Checking for good connector contact is also crucial, as oxidized contact points can trigger false faults. Ensure stable multimeter probe contact during measurement, as poor contact causing fluctuating readings may lead to misjudgment. If unsure, it's advisable to visit a professional repair shop.

[DeOmar]

My inspection process is simple and practical: Open the engine hood to check for any abnormalities in the appearance of the ignition coil. After starting the engine, use a temperature gun to measure the temperature of each cylinder's coil—significantly lower temperature may indicate a faulty one. After turning off the engine, remove the coil and use a multimeter to measure the primary coil resistance, which typically ranges between 0.4 to 1.5 ohms, while the secondary coil ranges from 5000 to 20000 ohms. If the measured value deviates by more than 20% from the repair manual, it is generally considered faulty. The spark test is also crucial: Connect the coil to a spark plug and ground it to observe the spark condition—a strong blue spark is normal, while a weak or no spark indicates a problem. Aging high-voltage wires can lead to misjudgment, so rule them out first. Finally, use the swap method to confirm the results.

[Cook]

The old method for testing ignition coils: Start the engine and unplug each coil one by one to listen for changes in engine sound. The cylinder where the engine sound changes the least when unplugged likely has a faulty coil—this is called a dynamic balance test. After turning off the engine, remove the coil and measure it with a multimeter. The primary coil resistance is usually within 1 ohm, while the secondary coil typically ranges between 6,000 to 15,000 ohms. Set the multimeter to the 20k ohm range for best results, and ensure good contact with the probes. For older cars, pay special attention to oxidized connectors, as they can interfere with test accuracy. A quick method is to measure resistance without removing the coil, but this is less accurate. Be cautious of high voltage when working on it—never operate barehanded. If a problem is found, swapping the suspected coil with a neighboring cylinder and retesting is the most reliable DIY approach.