86 johnson 4hp intermitent spark

new guy here familiar with engines in general. anyways i picked up an 86 johnson 4hp and it has an intermitent spark problem. you can here one of the cylenders kick on and off. i did some reading on this forum and set the points at .020" and installed new plugs and gapped them .030". i cut a half inch off the sparkplug wires where they go into the coils and reattached them making sure the coils were seated properly. problem still exists. engines runs great when both cylenders are firing. im stumped. are there suppossed to be any ground straps from the stator to the block? i dont see an ignition kill wire either. both plugs fire when pulling the engine over by hand. any help would be greatly apreciated. thanks in advance.

Re: 86 johnson 4hp intermitent spark

Are you sure it's an ign problem? Could be dropping a cylinder because of compression or fuel.
Use a timing light to confirm loss of spark on a cylinder and the recheck the coil, points and cond for that cylinder.

Re: 86 johnson 4hp intermitent spark

compression is at 95#/100#.
fuel pump was just rebuilt and is pumping fuel.
i have an auotmotive timming light. can this be used to check for spark? where do i connect the battery leads?

Re: 86 johnson 4hp intermitent spark

You need an inductive type light. Mine just clamps over a plug wire, I use an external battery source on small engines that do not have an electrical system.

Re: 86 johnson 4hp intermitent spark

cool. ill fill up my test barel and give it a try.

Re: 86 johnson 4hp intermitent spark

Let us know what you find.

Re: 86 johnson 4hp intermitent spark

did the test. its the top cylender thats missing. ran good until it warmed up.

Re: 86 johnson 4hp intermitent spark

If I remember correctly the front ign set, coil, points and cond, are for the top cylinder. Remove the flywheel and recheck your point settings. You could swap the coils and see if the miss moves to other cylinder. Make sure there are no cracks in the coils.

Re: 86 johnson 4hp intermitent spark

ive checked the points twice already and the coils LOOK fine. do you think it could be a condenser?

Re: 86 johnson 4hp intermitent spark

Could be, something is getting hot and failing. Like I said before, you can swap one componet at a time until the miss moves to the other cylinder, then you have found your problem. Only move one at a time, coil, cond, points, if you switch all at one time you will not know what was defective.

Re: 86 johnson 4hp intermitent spark

makes sense. eitherway, something needs to be replaced, so im going to start with the points and condencers since their cheap enough. thanks for the timing light tip. ill post a follow up when i get them in.

Re: 86 johnson 4hp intermitent spark

just a follow up;
i replaced the points and condencers and the problem did not go away. the local marina had new coils on back order so he sold me a used one for $15. this solved the problem and the engine runs great now. thanks for the help!!!