No Spark...'79 Johnson 100hp

[LAT67]

I have a 1979 Johnson 100hp outboard motor and I have no spark at the spark plugs. Before I begin changing the coils, power packs, rectifier or stator I was hoping to get some help from this forum, which I have heard great things about.

1. As I understand it, the stator produces the electricity to the power pack, which go to the coils and then to the spark plugs. How can I tell if my stator is functioning properly? Can I use a continuity tester to see that current is coming from the stator? If so, how would I do this? If a continuity tester cannot be use, what then would I use to complete the testing?

2. Assuming that the stator test comes out positive, how can I tell if my power packs are functioning properly? Can I use a continuity tester to see that current is coming from each of the power packs? If so, how would I do this? If a continuity tester cannot be use, what then would I use to complete the testing?


3. Assuming that the power pack test comes out positive, how can I tell if my ignition coils are functioning properly? Can I use a continuity tester to see that current is coming from each of the power packs? If so, how would I do this? If a continuity tester cannot be use, what then would I use to complete the testing?

Thanks in advance for your help.

 

[jtexas]

Re: No Spark...'79 Johnson 100hp

here's an ignition troubleshooting guide that covers all the components:
http://rapair.com/images/Downloads/Troubleshooting Guide 2006.pdf

You'll need a DVA adapter for your multimeter.

But first rule out the kill circuit: unplug the big red main wiring harness plug and turn the engine over by jumping the solenoid. If you get spark like that, troubleshoot the kill switch, key switch & wiring. the kill wire is black w/yellow tracer - grounds out the powerpacks when touched to ground.

Might want to disconnect & ground the spark plug wires for this test - if the engine starts with the harness unplugged, you'll have to manually choke it to kill it.

 

[ezeke]

Re: No Spark...'79 Johnson 100hp

The best way is to remove all of the spark plugs and use a tester set up with a 3/8 to 7/16 gap for each spark plug wire. With no load on the engine, the firing should be maximized and produce a snappy, sharp blue spark.

You can use a tester like the CDI one shown here: http://www.iboats.com/Cdi_Spark_Gap_...-view_id.38089

Or, you can make something simple with a board and nails. Or something like this:

 

[LAT67]

Re: No Spark...'79 Johnson 100hp

Thanks for the information.......I disconnected the main wire harness and jumped the solinoid. I now have spark from three of the four cylinders. If you were standing in the back of the motor looking towards the bow, the cylinder to the top left has no spark.

As for the results of the test, I am guessing my problem is somewhere from the key switch to the female end of the main harness correct? How should I proceed now?

As for the cylinder not firing, I swapped a known working coil and determined that I have one bad coil....for $21/coil I will replace all four to be safe as I am unaware as to the age of the other three.

Let me know how to now determine what parts are no good.

Thanks,

Larry

 

[jtexas]

Re: No Spark...'79 Johnson 100hp

Not too bad a deal, having three spare coils.

"Somewhere from the keyswitch to the ... end of the main harness" is correct. Somewhere along in there, that black/yellow wire is coming into accidental contact with ground. Switches are the obvious place to start.

When the keyswitch is in the "off" position, the black/yellow kill wire is connected to a ground wire. Your emergency kill switch (if so equipped) has the black/yellow on one terminal and a ground wire on the other. It's normally open, and closes when the lanyard is pulled. Could also be in the plug. Just have to get out the continuity tester & get 'r done.

good luck!

 

[LAT67]

Re: No Spark...'79 Johnson 100hp

To EZEKE...thanks for the info and the link.


To JTEXAS...thanks for the info. It will be a great addition to the owners manual for this outboard.

I agree three spares are better than one. I am also replacing the rectifier as it is $18.00..definitly worth it. I should have the coils and rectifier by the end of the week (6/22/07). I will move forward and test the ignition switch in the meantime.........so, I am off to, as Larry the Cable Guy says....."GET'R DONE!!"

I will report back to this forum as I move along and determine the condition of the ignition switch.

Larry

 

[LAT67]

Re: No Spark...'79 Johnson 100hp

Hello,

Today, I took the black w/yellow stripe wire off the key switch and with the main harness connected, tested for spark and got spark.

This means that the stop circut has a fault, right? How do I now determine if the fault is in the key switch, blackw/yellow stripe wire or the shift switch.

Talk with you soon.

Larry

 

[jtexas]

Re: No Spark...'79 Johnson 100hp

Set your multimeter for continuity.

Touch one probe to the "M" terminal on the keyswitch and the other probe to the other "M" terminal. If you have continuity with the key in any position other than "off", then the keyswitch is faulty.

Touch one probe to one terminal on the kill switch (safety lanyard) if you have one, and the other probe to the other terminal. If you have continuity with the switch in the normal (run) position, then the kill switch is faulty.

The shift switch (assume you mean the neutral safety switch) shuts off power to the keyswitch - if it were faulty, the starter solenoid & choke solenoid couldn't be activated.

 

[LAT67]

Re: No Spark...'79 Johnson 100hp

Hi ,

I replaced the key switch. The motor fired up on the third shot. So to recap, I found one bad coil so I replace all four leaving me with 3 spares. Because they were inexpensive, I replaced the soleniod and rectifier. I've tested the replace ones and they are now spares. The starter, power packs and stator are all very good and working just fine. I am now looking forward to getting out on the water to do some flounder fishing. Thank you for all your help!!!!!!!!