How to Test an Automotive Ignition Coil?

[ZoeyLynn]

There are three methods to test an automotive ignition coil: 1. Visual Inspection: Examine the ignition coil visually. If the insulation cover is cracked or the outer casing is damaged, it may absorb moisture and lose its ignition capability, requiring replacement. 2. Primary and Secondary Winding Open Circuit, Short Circuit, and Grounding Tests: (1) Resistance Measurement Method. Use a multimeter to measure the resistance of the primary winding, secondary winding, and additional resistor of the ignition coil. The values should meet technical standards; otherwise, it indicates a fault and requires replacement. (2) Test Lamp Method. Connect a test lamp to the two terminals of the primary winding. If the lamp does not light, it indicates an open circuit. To check for grounding faults, connect one end of the test lamp to the primary winding and the other end to the casing. If the lamp lights, it indicates a grounding fault. Short circuit faults are not easily detected with a test lamp. 3. Spark Intensity Test: To check the high voltage generated by the ignition coil, it can be tested on a test bench in conjunction with a distributor. Adjust the discharge electrode gap to 7mm, start at low speed, and once the ignition coil reaches operating temperature (60~70°C), adjust the distributor speed to the specified value (generally 1900r/min for four- and six-cylinder engine ignition coils, and 2500r/min for eight-cylinder engine ignition coils). If it can continuously produce blue sparks within 0.5 minutes, the ignition coil is in good condition.

[AliviaFitz]

When I have trouble starting my car, I usually check the ignition coil first. The most straightforward method is to remove the ignition coil and inspect its casing under light for any cracks or signs of scorching. Once, when my car had unstable idling, I discovered a crack in the ignition coil of the second cylinder. Next, I use a multimeter to measure the resistance value. The primary coil resistance is typically between 0.4 to 2 ohms, and if it's higher than this range, it's usually faulty. You can also perform a spark test by connecting the spark plug to the ignition coil and grounding it. If the spark is weak or appears red when starting, it indicates a problem. I recommend wearing insulated gloves during testing—last time I got shocked while handling it and felt numb all day. Usually, after inspection, the issues found are either aging of the coil with damaged insulation or poor internal wiring connections leading to insufficient current strength.

[LandonDella]

The most commonly used method I employ for testing ignition coils is the substitution test method. Prepare a confirmed working ignition coil and swap it onto each cylinder one by one for testing. Remember to first remove the fuel pump fuse to prevent fuel injection, then disconnect the ignition coil connector to be tested. Once, when my car felt sluggish upon acceleration, I used this method to identify a faulty coil in cylinder three. Using a multimeter is also practical for testing. To measure the secondary winding resistance, disconnect the connector first. The normal range is between 6,000 to 15,000 ohms. If it shows infinity, it indicates a complete open circuit. It's advisable to regularly inspect the rubber boots and spring contacts for oxidation, as poor contact in these areas can lead to decreased ignition efficiency. Paying special attention to these before long trips can save a lot of trouble.

[CadenRose]

Testing an ignition coil mainly involves three steps. First, inspect the exterior for any oil stains or burn-through marks on the casing. Last time during a repair, oil seepage at the coil base was a sign of failure. The second step is to measure the resistance; a primary coil resistance below 1 ohm is considered normal. Simply touch the two terminals with the red and black probes of a digital multimeter to get the reading. Finally, reinstall it on the vehicle and observe. Difficulty in starting or rough idling can usually confirm the issue. I've noticed that ignition coils in Volkswagen group vehicles are particularly prone to failure, so frequent checks are necessary after 50,000 kilometers.