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Electrical Issue 15R74S

B

Bullie

Regular Contributor
I have reached the end of my understanding again. It happens often. I am working on a 1974 Johnson 15. It has a bright blue snapping spark on the bottom cylinder and an erratic and weak to no spark on the top. The top plug was black and oily looking and the bottom was brown as is usual.

What I did:
I removed and cleaned/polished the points on both sides, set them to the correct gap, replaced the condensers. No change. Figured that was the problem but no. I then switched the external coil for the top cylinder with an old one I know to be good. Nothing. I reinstalled the original and decided to swap the wires from the bottom coil to the top. Bam! Same bright blue spark I was getting on the bottom cylinder. So, I eliminated the coil as the issue. I removed the flywheel again and checked everything I had done and looked for any abrasions on the wiring that might cause a short to the top cylinder. I removed the plate and checked the clamp on top and bottom, no damage that I could find.

How does the driver coil alternate spark to the sides? Like I said, I have reached the end of my understanding and need some help. Is it likely the problem?
 
Concerning the driver coil, can one side go bad? It has a wire going to each set of points. One side is working. One side is not. Is there a way to test the driver?
 
Update. I switched the points and there is no change. I have spark to the same cylinder. I checked continuity on the wires from the points to the ignition coils. They were the same. So, can one side of the driver coil go bad?
 
How many wires come out of the driver coil and where do the go ?? It's been quite a few years since I worked on one. A pic would help.
 
Maybe it's the lighting, but those points don't look clean to me. BOTH sets of points must be clean and properly set because both sets are involved in creating a spark to either cylinder. If you haven't already, remove the points, degrease them, and polish each contact shiny bright, then reinstall and set gaps. Even new points need to be cleaned.

The driver coil feeds both cylinders.
 
I have had the points off and polished them to a shine. I do see a little grease on the back of them in the picture but the contacts, and the area around them, have been cleaned with solvent. I have swapped them side to side. The condensers are new.

The magnets look good as does the flywheel itself. It isn't wobbling. I have had the armature plate off looking for abrasions in the wire. It is tight and doesn't wobble.
 
I did check it once but I will again. It has to be somewhere from the points to the clip connector on the ignition coil.
 
I have the kill button disconnected. I will try swapping the condenser. What would the odds be of replacing a bad condenser with a bad condenser? LOL Just my luck though.
 
Try to swap the wires going out to from the condensers to the coil pack, it is very possible to have a wire bad inside the insulation, and still read ohms through it, but wil not pass current.
 
If he's got a wire that "will not pass current" he should get a high resistance reading.

OP, have you had any luck in getting this motor to the point where that one spark is GONE, rather than weak?

You may also consider removing the red crimp sleeves from the wires to look for corrosion. When done, you can replace those with some Heat Shrink tubing.


CMOS
 
I haven't been able to get to that one for the past few days. Hopefully I can get to it tomorrow. I appreciate the help.
 
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