Johnson 120 Intermittent No Start

[FarmallM]

My Johnson 120 (model J120TLESB S/N G02569565) has been having an intermittent issue. It will run for 10 minutes to 2 hours (the longest I've run it without shutting it off) , but when it dies it will not re-start for 10 minutes to 3 hours. It always starts right up after extended stops, like overnight. I've installed a fuel/water filter that didn't solve the problem. I've checked venting the tank, but that didn't help. The fuel level doesn't make a difference. I was able to remove a plug and ground it while another person cranked the engine and didn't get any spark. I was also holding the plug when it finally started and can positively verify that there is adequate spark when it finally decides to start! How do I diagnose the faulty component? Is there one component that is more apt to cause total shutdown? Thanks
Marlin

 

[racerone]

Fact-----If the motor cranks over slow there will be no spark.----------So start with an inspection of the starter / battery / battery cables.----------Now most folks respond to this with a ----" my motor cranks just fine "-------------It takes time to learn / comprehend this stuff.

 

[FarmallM]

I checked the cables, battery condition & starter. All appear fine and engine normally starts almost immediately. After it has shut itself down and I've waited sufficient amount of time, it also starts right away. I notice no change in the cranking speed, even during the 3 hour wait (I tried every 15-30 minutes to start it, cranking approx. 5 seconds each time).

 

[racerone]

Well, I guess you need to do some more trouble shooting here.

 

[FarmallM]

I forgot to state clearly in the first post that the original problem was that the engine would die unexpectedly and THEN refuse to re-start. Sorry for leaving that out.

 

[jakedaawg]

Once it quits running and you can't get it to start do an open airgap spark check on all leads. I think you will find that you have something thats starting to fail when it gets fully warmed up. These can be tricky to find as you have to do the troubleshooting when it is actually screwing up.

Also have a set of amphenol jumper wires handy. After the motor shuts down and you do the spark check if you have no spark on all leads you will need to jumper 4 of the wires from the five pin amphenol connector on the engine harness leaving the blk/yellow unhooked and recheck for spark. In the end you will probably find a bad key switch/kill circuit or wireing that eventually grounds out somewhere or a bad pack but its best to properly troubleshoot instead of throwing parts at it.