What are the reasons for a car spark plug not firing?
2 Answers
Reasons for a car spark plug not firing: 1. Improper adjustment of the spark plug gap; 2. Oil accumulation on the spark plug electrode surface; 3. Cracks or damage to the insulator skirt; 4. Short circuit in the high-voltage wire; 5. Excessive carbon buildup on the spark plug; 6. Broken or detached electrode; 7. Insulation resistance of the spark plug is too low; 8. Erosion of the platinum contacts; 9. Weak spring tension of the platinum contacts; 10. Insulation breakdown or short circuit in the capacitor, rendering it ineffective; 11. Damaged ignition coil. Methods to check the condition of a spark plug: 1. A healthy spark plug electrode should be light yellow; black electrodes indicate incorrect air-fuel mixture ratio; 2. If it appears oily, it suggests a misadjusted spark plug gap or excessive fuel supply, or a short or open circuit in the high-voltage wire; 3. Black deposits indicate carbon buildup on the spark plug and bypassing.
I've seen quite a few cases where spark plugs fail to fire. The most common cause is definitely the spark plug itself - either the electrodes are severely eroded or too much carbon buildup has blocked the gap. In these cases, simply removing and replacing with a new spark plug usually solves the problem. Next is aging ignition coils - if the coil is leaking electricity or has internal short circuits, the high voltage can't reach the spark plug at all. Then there are loose wiring harness connectors or wires chewed by rodents, especially the section between the ignition coil and spark plug. Another often overlooked issue is a faulty crankshaft position sensor - if it's not working, the ECU won't know when to fire the spark. Finally, electrical circuit problems like blown fuses or poor relay contact can paralyze the entire ignition system. These are all fairly common issues. You can first check the spark plugs and wiring yourself, but if that doesn't solve it, I recommend going directly to a repair shop.
