1975 85hp spark problems

[fishhard]

I have a 1975 v4 85hp motor that seems to have all the original ignition parts. The problem I am having is an intermittent loss of spark to the number 1 cylinder when using a spark tester with a good battery and all four plugs removed. I have swapped coils with one that is firing fine and see no difference it has nothing to due with heat as even in the shop sometimes it works and a minute later it does'nt.
I also have swapped the #1 sensor input wire with the #3 sensor input wire, with these wires switched I still have good spark from the #3 coil output of the pack but still none from the #1 coil ouput: to my line of thinking this swap would mean I am getting spark from the #1 sensor and #3 sensors at the flywheel but not spark through the #1 coil at the power pack. Is this right? I do not have a neon tester or a DVA. I do have a good multi meter.

Question number two: 2 of the coils have small hairline cracks in the coils, these are not arcing out or leaking, should I A. seal them with epoxy B. replace the 2 cracked coils or C. replace all four.

After reading the posts on this site I know I am at the right place now I just need someone to verify my line of thought before shelling out the cash...
Thanks

 

[iwombat]

Re: 1975 85hp spark problems

If you've got cracks in the coils replace them.

You should also check the ground straps on the bracket the coils mount to. There should be a ground strap on each side of the bracket.

 

[fishhard]

Re: 1975 85hp spark problems

I forgot to mention I do have the factory manual but it only mentions the neon tester.

 

[fishhard]

Re: 1975 85hp spark problems

If you've got cracks in the coils replace them.

You should also check the ground straps on the bracket the coils mount to. There should be a ground strap on each side of the bracket.

Ground straps look fine I dont think they have been touched since new(still sealed with black "goo". If the grounds were bad I would probably be having the problem on more than 1 cylinder? I am by no means a mechanic the little I know I learned from reading posts on this site! Can anyone approve or disapprove my original train of thought? I don't want to just keep throwing parts at this to solve a symptom that I could be completely wrong about.