1970 40hp Johnson no spark on lower cylinder

[changetires]

Hello,

New to the forum. Been lurking around here for awhile but just now have a post to submit.

1970 40hp Johnson, no generator or altenator or stator, electric or manual start, has no spark on lower cylinder. Replaced points, replaced lower coil, replaced wiring harness that corroded and fell apart, finally got everything back together and still no spark on lower cylinder. Motor was running great down river the other day then I throttled back to idle by some boats and when I went back to WOT I only got half speed and 1 cylinder firing. I have also bypassed the vaccum cut off switch and this did not help. There is nothing else I can find in the Clymers to check for and this is my last resort. Can anyone help with this.

Thanks,
Ed

 

[F_R]

Re: 1970 40hp Johnson no spark on lower cylinder

How about the spark plug wire? They have a habit of arcing through where they are clamped to the armature plate. It will be a tiny pin hole through the insulation, barely visible. If it is not that, then you have to start with some resistance tests. Check back for more onfo on that, if needed.

 

[K.B]

Re: 1970 40hp Johnson no spark on lower cylinder

Welcome changetires!!

I have a '71 40 h.p. Evinrude.

Have you checked for spark with a check plug? Swapped coils to see if it chases to the top plug? You didn't mention changing plug wires while you were in there doing points. Did you? Should. Less grief later. Coils lined up correctly?

NOT razzing, just asking. Also check to see if one of the black wires to kill it is doing just that where it shouldn't under the flywheel. Good luck to you. Great motor. I love mine.

 

[byacey]

Re: 1970 40hp Johnson no spark on lower cylinder

I'm not sure when and if they changed the armature plate design, but if it's wobbly this could also affect ignition. Seeing that you changed coil, points and condenser, it's either point gap adjustment, oxide on the point contacts, wobbly plate throwing point gap out, shorted primary wire between kill switch and lower cylinder ignition coil, or HV wire arcing as someone suggested, and or fouled plug. I would check the HV end first with a spark gap tester.

 

[F_R]

Re: 1970 40hp Johnson no spark on lower cylinder

1970 has the improved armature plate mounting. That brings up another point: The armature plate on that one has to be grounded (there's a ground wire) because the mounting parts are non-conductive.

 

[changetires]

Re: 1970 40hp Johnson no spark on lower cylinder

Thanks for all the replies,

Yes the plate is grounded with a small portion of wire to the power head. I pulled the plug wires and found the lower cylinder wire had a small hole under the pinch clamp. I say small but it was big enough to stick the ohm meter probe in and get a reading with so it had to be arcing through it. Seeing as how its Sunday I will bet new wires for both tommorrow and put everything back together and see if that solves the problem. Motor runs great when its running. These were the original wires so I guess its time to change them anyway. The internal wiring harness was also toasted and those wires just fell apart when I was checking out the electrical system. Maybe this will put me on the road to recovery. I will post up sometime tommorrow or Tuesday when I get it back together.

Thanks again.

Ed

 

[byacey]

Re: 1970 40hp Johnson no spark on lower cylinder

I would say you found the problem. When it comes to high voltage often you can't even see the insulation breakdown point. It could be just a little pin-prick mark no more than .001" , but will arc through to ground.

 

[changetires]

Re: 1970 40hp Johnson no spark on lower cylinder

F R nailed it. Put two new plug wires on last night and now I have fire on the bottom cylinder. Went ahead and changed the upper on while I had the plate off. Gonna run it tommorrow at the river and see how everything goes. Thanks for all the help.

Ed

 

[changetires]

Re: 1970 40hp Johnson no spark on lower cylinder

Motor ran great.

Thanks for the replies.

Ed

 

[kbait]

Re: 1970 40hp Johnson no spark on lower cylinder

I work on older johnnyrude's part-time, and I ALWAYS change out the plug wires when working on under-flywheel ignitions! I bought a 100' spool from my marina for $55. I just got sick of scratching my head and pulling the flywheel off again.