Editing Reading spark plugs (section)
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===Other tell-tail signs of plug condition=== [[File:Autolite-hot6.jpg]] [[File:Saltandpepper7.jpg]] Shiny or glazed deposits: This occurs from excessive idling or rich idle condition leaving heavy soot deposits. If excessive and not cleaned or the idle air/fuel ratio corrected, these deposits can cause excessive porcelain temperatures as they oxidize, causing the glass to melt. This in turn can cause down-track popping through the exhaust. This glazing on the porcelain actually becomes a conductor and the spark will jump from the electrode to the porcelain resulting is a very weak, small spark if any spark at all. You will usually see splotchy deposits on the plugs after the run, either green or yellow in color along with the tell-tale shiny glaze. Remember, the porcelain should always have a chalky or dull finish. Base of threads sooty: This is usually a indication of the plug not being tight enough, allowing air to be pulled in to the chamber and air/fuel being pushed out. Change the plug, tighten to spec. This area should have a nice dark to medium gray color without heavy deposits. [[File:Rich18.jpg]] Black or brown specks: This is an indication of detonation which is caused by ignition timing that is too advanced for the air/fuel ratio or octane of the fuel. Detonation (an undesirable, uncontrolled combustion of the air/fuel mixture after the ignition event) causes the boundary layer of air within the cylinder to be disrupted, which in turn causes the components and surfaces within the cylinder to absorb heat from the combustion process and increase in temperature. The black spots are the result of oil deposits bypassing the piston rings during detonation and being fused onto the porcelain by the increased cylinder temperatures. Tiny beads of grey/silver material apparent on the porcelain are melted piston. Reduce the ignition timing, richen the mixture, increase the octane of the fuel or a combination of all of these to prevent this situation. {{Warning}}Do not underestimate the damage this condition can cause your engine. Correct this by whatever means necessary. [[File:AR3933-terry-wise-plug19.jpg]] Shiny little diamond like deposits: It may be too late, the pistons have begun to disintegrate from the heat and/or detonation. If the engine doesn't exhibit symptoms of a pinched rings or broken ring land (smoking exhaust, excessive blowby, low compression reading, excessive leak down), back up and start over with the tune of the engine by doing one or more of the following: *Lower the air/fuel ratio to a safe level *Reduce the timing *Use a colder plug heat range No color mark on ground strap: If your showing good color on the porcelain but the ground strap fails to show an indicator then your plug is too cold, go up 1 heat range. If the ground strap is showing a good color line but the porcelain is showing no color at the base then your plug may be too hot, drop down a range. I will use maybe 3 different ranges on one bank, make a pass and from those three different plugs determine which one is correct for the engine. [[File:How to read spark plugs10.jpg]]
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