Sorry........any sort of oscilloscope.......ignition scope, electronics bench scope, it does not have to be "much a one." Any electronics hobbyiest/ ham operators in your 'hood?
What this will do is allow you to see if the "open" time is enough to capture the energy that "should be" in the spark
Here's a quickie I searched off the internet
Notice that the plug fires showing as a horizontal line. The plug is "pulling down" the voltage because of conditions in the cylinder. Then they show "coil oscillations." These are the last of the dying energy of the coil AFTER the plug has pulled down and loaded down the coil so much that it just won't "jump" anymore, and not the coil is "petering out. FROM THAT POINT to "points closed" which in this is labled "control module again allows primary current to flow" that is the same as "points closing."
WHAT YOU WOULD WANT is to make certain that there is "some space" in that area as shown in this example........in other words if the points do not stay open long enough, they might close again BEFORE the plug has stopped firing----thus robbing the firing cylinder of possible spark energy. The point to the far right is at the same time as the point at the left whichs says "secondary voltage building." That is the point at "points open"
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