How to Test an Ignition Coil?
2 Answers
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.
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.
