What Causes a Spark Plug to Fail to Ignite?
2 Answers
Spark plug failure to ignite is caused by spark plug damage. Damaged spark plugs can directly lead to various issues such as leakage in the vehicle's ignition system, increased fuel consumption, and reduced power. The most significant problem is difficulty in ignition, which affects the normal operation of the vehicle. Severe spark plug erosion, including blistering at the top, damage, or melted and eroded electrodes, indicates that the spark plug is damaged and should be replaced. Methods to determine if a spark plug is damaged: Remove the spark plug and observe its appearance to assess its condition. A normal spark plug's insulator skirt and electrodes should appear gray-white, gray-yellow, or light brown. A properly functioning spark plug has a reddish-brown insulator skirt, with an electrode gap between 0.8-0.9mm and no signs of electrode burn. If the spark plug is contaminated with oil or deposits but is not damaged, it can continue to be used after cleaning off the oil and deposits. If the spark plug is severely damaged, showing signs such as blistering at the top, black streaks, cracks, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plug with a new one. Additionally, if the spark plug appears black as if smoked, it indicates that the wrong heat range was selected or that the air-fuel mixture is too rich, with oil creeping up.
The spark plug doesn't fire. I've driven several types of cars, and the common reasons are spark plug wear or excessive carbon buildup blocking the gap, causing ignition failure. Ignition coil failure is also a key factor; if the coil is aged or loose, it can't deliver sufficient electricity. Circuit issues such as blown fuses, damaged wires, or rusty plugs causing poor contact can prevent the spark from occurring. A weak battery or unstable alternator voltage can also disrupt the ignition system, especially in winter when low temperatures can trigger problems. Fuel issues aren't a direct cause, but an overly lean air-fuel mixture can make spark generation more difficult. I recommend checking the spark plug gap and cleaning carbon deposits every 10,000–20,000 km to prevent sudden stalling while driving. If undergoing major repairs, don't skip testing the ignition coil and battery voltage—it saves money and hassle.
