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Discussion Starter · #1 ·
1987 4.3 points ignition replaced by Hot Spark brand electronic ignition. Old coil tested bad so I replaced it. I disconnected shift interrupter and tach wire from coil just to eliminate those possibilities, still no start. I disconnected tach wire because even though tach probably works...I have no idea what gauges work yet.

What it is doing however, is different than I have experienced before. usually it is spark or no spark. I hook my timing light to wire that is from coil to dist cap. I crank the engine and get spark for about 1-2 seconds then nothing. If I let it sit (or monkey with something on it for a few minutes) and try it again, same thing....spark for a second or two, then nothing. My SELOC or Clymer doesn't cover anything like this and I looked at my downloaded version of the factory service manual from OMC and while it might cover it, I did a "control F" and found nothing.

Usually I would say this is the ICM knowing the coil is good (I did test the new one just to be sure) OR a short in the ignition circuit. Of course all the tune up stuff is new. The neutral safety switch prevents power to starter motor, not spark like an outboard so if it turns over, you are in neutral.

I have never had this engine running since it is new and I just got it installed and put back together. The old block had an internal crack however I did start it and it ran great on the hose...this was 2 years ago with points still installed and old coil of course.

As always I appreciate it
 

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Red X Angler
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Sounds like a ground short to the module possibly.
 
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Discussion Starter · #3 ·
One thing I didn't check is voltage to coil WHILE CRANKING. Curse of working on it yourself. If I have low voltage while cranking to + on coil that means I've probably got a bad ignition/key switch right?
 

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Discussion Starter · #4 ·
For anyone who may benefit from this info, I will post my findings and a couple steps I went through to figure out my weak spark/no spark condition.
Initially tested coil: zero resistance in primary and secondary--replaced coil (still no spark)
Tested voltage again at + side of coil koeo: 12.4v
Tested voltage at + side of coil while cranking: 9v initally, dropping to 5v after several seconds (told me I had lower than prescribed voltage)
To isolate the issue I bypassed ignition/key switch part of the ignition circuit by using 14 AWG wire and jumping from + battery to + coil. Turn the key to START. Spark was present.
This told me that part of the ignition starter bypass circuit was "bad"
Looking at the diagram in my SELOC I was able to track down a purple wire that went from starter solenoid to + side of coil. Checked continuity at the POST where it is attached to solenoid and other end where it terminates at + side of coil. I had no continuity.
I was just going to run a new wire but thought I'd removed both ends, clean thorougly and try again.
This resulted in a good strong spark.

You all know the moral of the story
 
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