05" gap which I guess fits in there with the 45kv that my Merc Service manual says my '02 90 hp puts out but that's surface creep across a non conducting surface.like a clean ceramic insulator. 1" per kv (surface creep) which would give you 40 to 50 kv for. Run it for years and the track is still there, but bigger, yet it runs smooth as silk.īeen heavily involved in high voltage and ignition type (pulsed) systems all of my professional life but fail to figure out how a really fast CDI (microseconds to 10's of microseconds) can fire the plug before the firing energy gets shortedout by the resistance of the carbon track. Put in new white ones, run for a few minutes and pull out a carbon track. Hey Rodbolt, that's one of my curiousities with surface gap plugs. ![]() My eyes are getting dim so I use the correct diagnostic tool. It will leave distinctive tracks ,normally, but the tech did not catch it.Ībout 3 1/2 hours was spent on a defective spark plug test.Ībout the only way to accurately find this problem was a Kv tester or an experienced eye. it was traveling from the center electrode down the insulator to the plug shell. ![]() more than enough to trigger his light but not near enough to spark the plug gap.Īs the porcelian around the center electrode was contaminated and carbon is a fair conductor the electrical current was simply taking the path of least resistance. His next step for reasons he could not explain as to inspect valve clearence.Īt this point I intervened and stopped him.Ī Kv test showed #6 plug had fouled with a firing voltage of about 2KV. a leak down test and spark test had revealed no issues. One of the young tech´s tested it, spark on all 6 according to his inductive timing light and spraying fuel down the air intakes made no difference. customer complaint, runs well starts easy but lacks power. it can lead to erroneous results costing valuable testing time.Īn example, F225. ![]() I dont like the timing lamp method of spark testing. The reason for the various air gap specs when testing ign at cranking is due to the fact that in actual running combustion presures the electrical load increases.Īs the load increases so does the voltage required to make an arc acrossed the electrodes.Īs th firing voltage increases and electricity is lazy if there is a defect in the ign coil or secondary wiring eventually the arc will be to ground outside the plug gap. Re: Does an inline spark tester adequately show the quality of spark?ĭepends on the inline tester, some are adjustable out to about 11/16ths gap.
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