1980 Johnson 35hp Nil Spark problem

[Dave Gould]

I am still fighting the very intermittent nil spark prob on my motor. This prob is very intermittent, she dies maybe only one time in 10. Kill sw and wiring all good, pwr pack replaced, all other wiring checked OK. Ign coils OK. Am wondering about the trigger coil thingies under the flywheel. Have had flywheel off, wiring looks good, but the coils are encassed in the green plastic with the charging stator windings, so only way to check them is electrically with a digital ohms meter from the bigger rubber plug.Can anyone tell me anything about these coils, could they cause my prob? Know how many ohms each coil should be etc. Any other clues?

 

[WillyBWright]

Re: 1980 Johnson 35hp Nil Spark problem

Multiple coils won't fail at the same time. Could be water or corrosion in your key switch, corroded connections on the motor (especially grounds), or maybe a screw point is stabbing your wiring harness in the gunwale.

 

[Dave Gould]

Re: 1980 Johnson 35hp Nil Spark problem

Thanks Billy, I have previously elliminated the key sw or wiring harness as source of the prob.<br />Today when she was running fine, I stopped her, disconnected the bigger rubber plug to measure wires going into the gen stator/trigger coil assy.<br />The 2 middle pins were showing about 50 ohms which looks like a good reading for a trigger coil. Later when she died I found this resistance had shot up to 400ohms, so maybe I have an intermittent fault in a trigger coil. I dont know what the 2 outside pins of that plug go to. Does anyone know if there is 2 or only 1 trigger coil under the flywheel.

 

[G DANE]

Re: 1980 Johnson 35hp Nil Spark problem

I has one trigger coil only.

 

[OBJ]

Re: 1980 Johnson 35hp Nil Spark problem

Dave....just a shot in the dark....did you try moving the wire harness' around as the engine was running? It's possible you have a break or near break in a wire that opens only when in a certain position. Try moving the wires from the stator first as these move a lot as the engine runs. <br /><br />Keep us posted.

 

[Dave Gould]

Re: 1980 Johnson 35hp Nil Spark problem

Thanks G Dane and Jim. yep I am learning plenty about the ign electrics on these O/B,s. I realise now that there is 1 trigger coil and also an excitation coil for the pwr pack. Both potted in plastic with the alt stator windings. If I disconnect the bigger rubber plug I can take resistance readings of these 2 coils, the 2 outside pins show about 450 ohms (I believe this is the exitation coil) and the 2 inside pins show about 50 ohms.(this is the trigger coil). On my O/B, when she dies, this reading goes way up. She runs OK when back to around the 50 ohms. The wire harness is good, problem seems to be inside the potted assembly. I will change this next. If I had known what I now know before, I could have saved myself hrs of work. hopefully this info will help someone else.