How to Check if a Spark Plug is Good or Bad?
2 Answers
Spark plug inspection methods are: 1. Unscrew the spark plug and place it on the cylinder block, then test for spark with a high-tension wire. If there is no spark or the spark is weak, it indicates that the spark plug is leaking electricity or not working; 2. Let the engine idle and carefully listen for changes in engine speed and sound. If the changes in speed and sound are noticeable, the spark plug is functioning normally. If the changes are not noticeable, it indicates that the spark plug is in an abnormal state. The function of a spark plug is to introduce high voltage electricity into the combustion chamber, causing it to jump the electrode gap and produce a spark, thereby igniting the combustible mixture in the cylinder. The main types of spark plugs include: standard spark plugs, insulator-protruding spark plugs, electrode-type spark plugs, seat-type spark plugs, pole-type spark plugs, and surface-gap spark plugs.
With years of experience in cars, checking spark plugs is quite simple. First, pull them out and inspect the electrode: the normal color is brownish. If there's black carbon buildup, the electrode is eroded and rounded, or the gap is too large (measure it with a gap gauge; the standard is 0.7-1.1mm), it's likely faulty. A gap that's too large causes weak ignition, leading to slow starts and rough idling; if it's too small, it may get stuck. Excessive carbon buildup can be carefully brushed off, but avoid forcing it to prevent cracking the ceramic layer. Symptoms like sudden increases in fuel consumption or poor acceleration also indicate issues. Remember to turn off the engine before working on them—safety first. DIY checks can save you money instead of replacing them unnecessarily. Regular cleaning and maintenance can extend the spark plug's lifespan and prevent breakdowns on the road.
