Spark Plugs
Common Spark Plug Conditions.pdfSpark Plug Analysis
In Groups of no larger than 4, Choose an engine that was identified yesterday to research the spark plug socket size and torque specifications.
Show your findings to Mr. Nannan to receive the tools to remove and reinstall the spark plug.
EACH group member must remove and reinstall their own spark plug. Be sure to document (through picture images) which cylinder the spark plug was removed from!!!
When you remove the spark plug, take a picture of the end and determine if there is an issue with the engine based on any deposits on the spark plug.
Submit your findings in google doc through google classroom including sources and images that support your assessment of the engine condition.
What will happen if we connect a 12V battery directly to a spark plug?
Make your educated guess on the google form in our classroom!
What are the main issues with spark plug gap settings?
Narrow-gap risk: spark might be too weak/small to ignite fuel;
Wide-gap risk: plug might not fire, or miss at high speeds;
Narrow-gap benefit: plug always fires on each cycle;
Wide-gap benefit: spark is strong for a clean burn.
A properly gapped plug will be wide enough to burn hot, but not so wide that it skips or misses at high speeds, causing that cylinder to drag, or the engine to begin to shake. If a spark plug has eroded you’ll note how the center electrode (dark bump) had been a cylindrical rod, and the top ground electrode (like a claw) formerly had square edges.
As a plug ages, and the metal of both the tip and hook erode, the gap will tend to widen. Therefore, many experienced mechanics often set the gap on new plugs at the engine manufacturer's minimum recommended gap, rather than in the center of the specified acceptable range, to ensure longer life between plug changes.
On the other hand, a larger gap gives a "hotter" or "fatter" spark and more reliable ignition of the fuel-air mixture. In addition, a new plug with sharp edges on the center electrode will spark more reliably than an older, eroded plug. As a result, experienced mechanics also realise that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs. Subsequently, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace or re-gap the plugs much more frequently, as soon as the tip begins to erode.
A hot plug has less insulation running down the center electrode which exposes it to the heat of the cylinder head.
A cold plug has more insulation around the center electrode which protects it from the heat in the cylinder head.
