Is there a way to test a CDI unit? (696-85540-12 - 1986 8hp 2cy)

[SteveVT]

More adventures with my 1986 Mariner 8hp 8M (manual) 6GI (Yamaha built). Had a great day going up and down river fishing, but she died at the very last moment coming into the dock, and couldn't be re-started. This time an ignition problem. No spark on either cylinder.

I've pulled the coil and tested resistance. On the primary side it's about 0.2 ohms (my meter isn't able to get more accurate than that) and on the secondary side (between the two plug wires, it's about 3600 ohms. I think those values are about what they are supposed to be.

I tested the On-Off Switch (really a kill switch- short to ground type) with the white wire disconnected from the CDI unit and connected to my multimeter, and the switch is definitely good. "On" is open on the white wire, and "Off" connects the white wire to ground.

I also tried to start the motor by disconnecting the white wire, to eliminate the kill switch and again, no spark.

So that pretty much leaves the CDI unit, or the trigger or power coil. My question is, how can I determine which it is?

I'm attaching a schematic from a mostly similar Yamaha, with a couple added notes about what I've tested and the values I got so far.

Thanks for your help in advance!

 

[SteveVT]

Is there a way to test a # 696-85540-12 CDI unit? (1986 8hp 2 cycle). I have a multimeter, and power supply.

 

[99yam40]

service manual should have the specs for the input and out put of the CDI.
but you will need the proper peak reading meter made for these ignition systems.
or you can buy an adapter and use you regular meter

 

[SteveVT]

service manual should have the specs for the input and out put of the CDI.
but you will need the proper peak reading meter made for these ignition systems.
or you can buy an adapter and use you regular meter

Thanks for that 99yam40. I found a couple of useful Dangar marine videos explaining troubleshooting the cdi system, and also one on building a DVA. I'm sending for one rather thn building, since the cost seems to have come down enough to make it worthwhile. I have some specs for the DVA voltage and also the static resistance on the trigger and charge coil(s). I guess you have to just assume the CDI unit is at fault by a process of elimination -- essentially testing all the coils?

I don't have specs for the CDI's output to the ignition coil -- as a guess should that be something near the output of the charge coil? In my case the output of the charge coil should according to manual be > 110V. So I'm guessing the CDI output to the ignition coil should also be that or better. I'm guessing the CDI unit doesn't step up voltage, just charges a cap with what it gets as a peak from the charge coil before sending that to the ignition coil.

This was the helpful video I found fr CDI troubleshooting.....in case someone has the same question I do:

 

[SteveVT]

I have another related question -- if one of the two spark plugs in my 2 cylinder engine is bad, will that prevent the other spark plug from firing?

The reason I ask is that there's a single coil for both plugs, and according to the Dangar video, Both plug wire outputs are connected internally in series to one secondary winding of the ignition coil. If there's a break in that anywhere in one plug or wire, does that stop both plugs from firing?

 

[99yam40]

that is true on waste spark systems

 

[SteveVT]

Thanks 99yam40, that gives me something else to check. Maybe I've been mistaking the problem of no spark in either cylinder by assuming it had to be coils or CDI. It could actually be a bad spark plug. Nevertheless the DVA is coming in case it isn't a plug.

 

[SteveVT]

I've opened this question on the Yamaha forum, since it is in fact a Yamaha under the hood, and no responses here.

 

[99yam40]

not many people have that old of a motor anymore.
salt and age get to them sooner or later

 

[GA_Boater]

I've opened this question on the Yamaha forum, since it is in fact a Yamaha under the hood, and no responses here.

Is 99yam40 a dead fish. Give it a chance for some replies.

 

[SteveVT]

Weird, I posted that on the Mercury Mariner forum, not here. Now the thread it was in has been deleted, and it seems to have been moved here for some reason.

Anyway, it certainly doesn't apply to you guys! I'm very happy with your responses!!

I'd appreciate it if someone deletes that post. I can't, and it makes no sense here.

 

[GA_Boater]

Weird, I posted that on the Mercury Mariner forum, not here. Now the thread it was in has been deleted, and it seems to have been moved here for some reason.

Anyway, it certainly doesn't apply to you guys! I'm very happy with your responses!!

I'd appreciate it if someone deletes that post. I can't, and it makes no sense here.

I did because we don't like multiple threads on the same subject, so I just chased it around the forum and combined it into a single thread. Deleting the original serves no purpose except to introduce confusion.

 

[SteveVT]

I'm glad you deleted the older unanswered thread on the Mercury Mariner forum, since I wanted to delete it myself but am not permitted to delete my posts on the iboats forum.

But I don't get why you moved my post here to the Yamaha thread, and then writing "Is 99yam40 a dead fish." Uh, no he is not, nor was I ungrateful for his help thanking him twice, nor unhappy with the speed of response.

Oh well, nevermind. I'm grateful for the help I've received here, bottom line.

 

[boscoe99]

 

[SteveVT]

Thanks kindly boscoe99. After I received my DVA converter I checked out the readings on all under-flywheel coils and the ignition coil. They were all within acceptable range. I changed out the spark plugs. Still No-go. Finally the replacement CDI unit I had sent for arrived. Replacing that restored the spark, and the engine now runs perfectly again.

I'm glad I do have the DVA now, and can check for any problems in future by not just throwing ignition parts at the system, but performing meaningful troubleshooting in advance. I thank all who responded in this thread -- your help was invaluable!