1980 70 hp power pack not firing one cylinder AGAIN?

sbklf

Petty Officer 2nd Class
Joined
Oct 26, 2006
Messages
190
I installed a 1980 Johnson 70 hp power head (don't know the history of it but it has good compression) on my motor. The first thing I did was check the spark. I found the top cylinder not firing.
-I then tested the resistance of the trigger coils and they were all in tolerance (#1 was 15, #2 was 17 and #3 was 18 ohms).
-I then tested the coils (OK), ignition switch (OK), the power pack/trigger coil and the power pack/coil connectors (OK). I tried all combinations of trigger outputs to power pack inputs and outputs to coils, name it I tried it and confirmed that all was OK except the power pack?s #1 circuit will not fire a plug.
-I borrowed a power pack and with it got good blue spark on all cylinders 1, 2 and 3.
-I then test ran it in the water, it was a dog. When I got back I again checked the spark; #1-No spark, #2-Blue spark, #3-Blue spark.

It seems coincidental that #1 failed again, like something is taking that circuit out. Someone told me to check the voltage on the black/yellow wire to the power pack; I will look at this next. If I could afford it I would purchase a timing plate, power pack and one ignition coil just to be sure but that would cost almost as much as the motor is worth.

Could a bad ignition coil or a bad trigger coil take out one circuit of the power pack?
Any ideas on what is most likely the problem?

Thanks, Kevin
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1980 70 hp power pack not firing one cylinder AGAIN?

Good clean tight electrical connectios are a must on your engine. Make sure all grounds are clean and tight.
 

petryshyn

Commander
Joined
Oct 3, 2001
Messages
2,851
Re: 1980 70 hp power pack not firing one cylinder AGAIN?

a bad coil or open plug wire can take out a pack.....
 

James R

Commander
Joined
Feb 1, 2007
Messages
2,679
Re: 1980 70 hp power pack not firing one cylinder AGAIN?

It may be just a bad plug wire or connector. These OMC motors do seem prone to plug wire or connector failure.
 
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