Yamaha 99 ignition mystery

"I have an intermitant problem

"I have an intermitant problem. My 97 Yamaha 9.9 runs flawlessly (95% of the time) or not at all. Once in a great while, it will not start and has no spark at all. I think yamaha fires both cyls with one coil in a configuration that requires both plugs to be grounded to get spark in either (just so you know that I know that). Last week - no spark. This week when I went back to troubleshoot - it works great. Resistances through pulser coil and charge coil match book values (measured on a day when it was working). Any ideas on this all or nothing phenomena?

-Scott"

"Scott, perhaps you could post

"Scott, perhaps you could post your model number as well.

I looked at the diagrams for the various models of 97 9.9's and they all seem to have two coils - but unlikely both would intermittently quit together anyhow.

Have you checked the various switches (neutral safety, kill, start (if elec)) when you have "no spark"?

Any of those would totally ground out your ignition - so something to check out..."

"Yes, I have checked or defeat

"Yes, I have checked or defeated the kill button and the safety switch attached to the tether.

I dont have model number with me at the moment but I think the schematic in my Seloc manual shows most of these two cylinder motors with the secondary coil circut going through one plug, through the cylinder head, through the other plug then back to the single coil.

One other possibility would be the oil pressure switch. I think it is suposed to kill the ignition if there is no oil pressure. I did not check that. That is probably also a normaly open that closes to ground to kill ignition. Thinking as I type this, that is a sound hypothisis! each time it didnt work, it failed to start! It did not die while running. The oil ppressure switch has to either function or not when the motor is first started. ???? I will have to look at that next (but with a problem so intermitant how can I know)

Beyond that,I wonder if some solid state thyristor in the CDI can be intermitant like that.

Thanks for helping me think.

-Scott"

"Scott, you may simply try dis

"Scott, you may simply try disconnection the oil switch the next time it won't start.

I would think if the problem was with the CDI that it would not work at all for you..."

check the grounds on the cdi b

check the grounds on the cdi box and coil
it is called a Siamese coil
fires both at the same time but the stronger spark goes to the cylinder with higher compression