1993 Johnson 8hp no spark to either plug

[MJDoriski]

Hello Everyone, looking for information on this issue.

From what I can determine the parts within are:
dual spark plug coil pack
power pack
AC charging coil
Ignition sensor
recoil
kill switch in handle arm.

Using a Digital volt meter checked the spark plug coils
ground to plug connector 300 ohms
ground to secondary point 1 ohm

The original one had some cracking on the back side replaced but the ohms values are the same between each.

kill switch changes state open to shorted and vice versa
The ignition sensor coil measures 39.3 ohms. white/w/black stripe and black/w/white stripe wires.

AC Coil brown / brown-yellow 880 ohms when pulling recoil measure 33V AC

somewhere I read 500 ohms and 150 Volts. If this is true I'm thinking the voltage is not enough to trigger the spark from the power pack.

Anyone confirm what the ohm is on the AC charging coil and what voltage should be measured on a pull of the starter rope ?

 

[racerone]

My bet is you need a new powerpack.

 

[MJDoriski]

I thought that as well, forgot to mention that the dual coil pack and the power pack have been replaced with no change in spark plug able to spark. I'll see if I can find and post, the information regarding the AC Charge coil having x amount of ohms and what was expected for AC voltage in the 8 hp model. If it was 500 ohms and 150 V, then my 880 ohm and 33 volts is pointing to the AC Charge coil. I'm glad its a solid problem, but very odd the motor ran flawlessly for the first few times out this year. Then failed so abruptly. I guess that is the technical term "It Broke".

 

[racerone]

Well, if you forget to post what you have or have not done

 

[MJDoriski]

Hello,
Here is a two page pdf that shows some relevant information. Pretty accurate, with the coils, wiring, connection plugs etc.
Second page is from another resource that allowed me to get some measurements & checks.
From what I can check, the AC coil ohms / voltage is not adding up. This is a small 8HP with a pull cord start. How much voltage can you get from a few rotations of the magnetic's ? I'm capturing 33 VAC on the DMM.
I did not have this diagram when I started, but worked back from the spark plug. After replacing the two higher possible parts the dual coil spark plug pack and the power pack. With no change in outcome - I found this diagram it appears to me that the magnets rotate around the AC coil which sends that voltage to the power pack and when appropriate, the power pack releases to the dual spark plug coil which is a step up xformer, this voltage allows the plug to spark and all is well. The neutral switch is mechanical from what I can determine, a physical stop on the recoil puller, when in a gear fwd or rev a lever pops out stopping the puller from rotating, in neutral its flush allowing the rotation. The kill switch changes states when depressed and released. Based on the write up the ignition sensor has the correct ohms.
Like many just helping out a fellow boater and fisherman get back on the water. I appreciate anyone's time to comment, their knowledge in marine repair and helpful pointers. Its a great little motor, runs smooth but the owner only had it a short time before this happened.

 

[MJDoriski]

Update:
The new charge coil arrived, better resistance 546 ohms vs the 890 off original. The outcome did not change no spark. The voltage went up from 33 volts to 47-52 volts AC on the pull coil start, Monitoring the output of the AC coil brwn/ brwn-yellow.
Revisited the kill switch and kill switch circuit. The switch it is not always going to full open, after 20-25 push buttons it varied from 10-35 ohms to full open. to bypass this pulled the black wire out of the plug connector. Finally had spark to plugs. several times while testing the top plug not always firing. found the plug wire not always passing the continuity check on meter.
summary: at this point have intermittent plug wire, and kill switch intermittent not full open. Will be providing a final update once everything is solid and working.

 

[MJDoriski]

All, the motor is back to working.
Although they do not go bad often, the kill switch on tiller handle when plugged into the circuit grounds out and no spark.
Bypassed with a different switch and motor runs fine. Did replace the one spark plug wire that doesn't ohm out consistently.
Thanks to all. happy boating.