1986 70 hp Johnson no spark

[midsized johnson]

I let my motor sit for a while (several years), went back through it and overhauled the carbs. Took it out and it ran great, but on the way in, started missing as if it was running out of gas. I assumed the pickup in the new fuel tank was set a bit high and starved it for gas. I got it home and it ran fine when I flushed the motor. Anyway, next time out, no spark when I tried to get the boat off the trailer. Took it home, still no spark, pulled the tach wire harness off and it fired. Took it back out and would not fire when put in the water. It's become an intermittent problem as far as getting it to run in the driveway. Sometimes no spark, sometimes runs like a bat out of hell (in the driveway, not in the water). I disconnected the wire harness and jumped the starter and got it to run, hooked the wire harness up to kill it, then it would start with the key. I replaced the wire harness and the remote control (friend gave me an old remote control unit). I replaced the power pack with OMC product and that didn't help. We jumped across the starter and got it running, then hooked up the wire harness again and it was running good. Checked spark and it looked really strong.
This afternoon, I put the lower unit in a trash can full of water and again, no go. I'm guessing the next possibility is the stator or trigger coil? I've got an old powerhead laying around with stator/coil assembly in unknown working condition. My question is, since this is an intermittent problem, will testing the stator/trigger coil with a test tool tell me anything, or am I better off just replacing them? Maybe I should run the cranking tests with the lower unit in the water for the back pressure?
Thanks in advance for any help.

 

[durban]

Re: 1986 70 hp Johnson no spark

test your stator the 2 wires comeing from the stator to power pack disconcet first . set your meter on low ohms range test across them you should get a reading of +|- 0.7 ohms for a 9amp stator , then set your meter on a high range & test for resistance on each wire to earth , you shouldnt get a reading if you do then the stator is trouble some .

 

[LongLine]

Re: 1986 70 hp Johnson no spark

Check all your pin connections. I had "messed with" my engine nearly all summer trying to find out why I had poor spark. Replaced power pack, coils, wires, plugs, tested trigger & stator but still had problem. Finally took it to a mechanic & he replaced a pin in one of the connectors then seated it properly. What a difference.

Tom B.
(LongLine)

 

[wanty9999]

...

 

[midsized johnson]

Re: 1986 70 hp Johnson no spark

Check all your pin connections. I had "messed with" my engine nearly all summer trying to find out why I had poor spark. Replaced power pack, coils, wires, plugs, tested trigger & stator but still had problem. Finally took it to a mechanic & he replaced a pin in one of the connectors then seated it properly. What a difference.

Tom B.
(LongLine)

I'm thinking it's along these lines. I can get it to run, but can't keep it running or it won't start at all with backpressure on it in a test tank or the boat ramp.
I'm going to look at the fuel pump when I can get back to it. I'm wondering if there isn't some gunk in there. I doubt it's causing the problem, but it won't hurt to clean it!

Thanks for all the input guys.

 

[midsized johnson]

Re: 1986 70 hp Johnson no spark

I found a wiring harness for a '93 70 hp Johnson. A local "guru" says the red plug on the wire harness can leak off and cause the issue I'm having.
Does anyone know if this will be compatible with my '86?
I've replaced the stator and the trigger coil with no luck. Fuel pump looked nice and clean on inspection with fuel getting to all carbs. I checked the spark, plug by plug, and had what looked like yellow spark on top and bottom with no spark on number 2 cylinder.

 

[Home Cookin']

Re: 1986 70 hp Johnson no spark

One way to look for shorts is to run it at night and look for sparks. Look around the controls and under the console, too.

Fuel and electrical problems can devilishly imitate each other. While chasing a ghost on my 1987 70 first thing was to run off a remote (portable) tank to test the fuel and fuel system to the motor. Go through the connections for air leaks (but that's typically a high-speed problem).

I was dropping one or two cylinders while running. I took a mechanic out with me on a run . he pulled the cover off the carbs, then sprayed fuel in with a windex bottle of premix. That had no effect so we knew it was electrical.

Tried pulling plug wires but that didn't answer it. I had already tried a new power pack and that wasn't it (also new plugs and new wires). So next suspect was the coils. The problem was in the top cylinder so we swapped the coils and the problem followed the coil (and they can malfunction with heat when they get old). I put in a new one--actually two since I'd sometimes drop 2 cylinders. That (knock wood) fixed it.

We thought we fixed it just by removing and reinstalling the coils, checking the ground connection--you might look at that before throwing parts at it.

In your case, swap the coils (top and center) and see if the no-spark follows it. If it runs fine after the swap you may have had the ground problem. if not replace the coils.

 

[Will Bark]

Re: 1986 70 hp Johnson no spark

This just a thought; My friend has a 77 70HP Johnny which was difficult to star tand would take many tries to start before it did(maybe) until his starter finally quit. We took it off and he carried it to repair shop who put new brushes in and generaly cleaned it up and greased it. Put it back on motor and when he hit the starter the thing started immediately; turned out the starter was not spinning the engine fast enough to generate a strong enough spark to fire. Has not failed him since. Just a thought.This something Joe Reeves and F_R preaches.

 

[midsized johnson]

Re: 1986 70 hp Johnson no spark

Thanks for the thoughts/ideas. I missed these last two posts. I put an old stator, trigger coil and flywheel on with no result, put the original assembly back in and cut the kill switch wire in an attempt to isolate the problem as being with the wiring harness. No spark at all on any cylinder. Have not checke the pin connectors, but visually, they appear to be okay.

 

[midsized johnson]

Re: 1986 70 hp Johnson no spark

Thanks for the thoughts/ideas. I missed these last two posts. I put an old stator, trigger coil and flywheel on with no result, put the original assembly back in and cut the kill switch wire in an attempt to isolate the problem as being with the wiring harness. No spark at all on any cylinder. Have not checke the pin connectors, but visually, they appear to be okay.

Update: Replaced stator, flywheel, trigger coil with yet another scavenged 70 hp. Plenty of spark now! Runs like a scalded-*** ape. Pretty sure the culprit was the trigger coil.
Again, thanks for the replies and suggestions.