Spark but no spark regarding rear cylinder 1968 Harley Davidson Electraglide
12-08-2012, 04:43 PM
#1
Le Mans Master
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Spark but no spark regarding rear cylinder 1968 Harley Davidson Electraglide
When the spark plug wire is snapped onto the plug, nice and snug, the plug doesn't fire, and the bike runs on the front cylinder only. When the wire is hanging on the plug wavy gravy, the plug fires, and the bike runs fine. I tried different wires on the plug, and I tried a different plug, and even though the resistance of the coil tested good with a fluke, I swapped it out anyway with a coil from another bike I have.
What do you think?
What do you think?
12-08-2012, 07:00 PM
#3
Le Mans Master
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Sure, and thanks for asking. By hanging I mean the inside of the wire boot is resting on the tip of the plug and isn't snapped onto the plug's end. The spark is jumping onto the plug, kind of like the spark is shorting-out onto the plug. Am I making any sense?
12-09-2012, 05:53 AM
#5
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Swapped out the coil even though I tested it with a fluke meter- changed out the condenser (forgot to mention that in the OP), and changed out the wires. The (bad) plug fires ONLY when the spark is allowed to jump from wire to plug.
12-10-2012, 12:02 PM
#8
Race Director
Not only have I seen this before, I have seen it on all kinds of engines. What is happening is when the plug wire is hanging loose you are in essence creating a larger gap than the one at the spark plug. Which takes higher voltage to jump the gap which in turn makes more voltage at the spark plug. Since you have replaced plug and wire and checked coil I would suspect something inside the cylinder. A lean condition, low compression tight or leaking valve could be what is happening. Something that would require higher voltage at the spark plug. A coil will only put out in voltage what is required to jump the gap. By holding the plug wire away from the plug you have created higher voltage. I hope this helps.
