Not your usual "no spark" problem, '87 Yamaha 9.9 , 4 stroke

[pemmink]

I've been following this forum for years and have found a wealth of great information here. Thanks to all.
I now have a problem that i just can't figure out.
With the plugs removed they won't spark if they are grounded to the engine block. They WILL spark if they are held away from the block and about 1/2" to 1" apart. When I do this a healthy spark jumps across the electrodes AND between the plugs' metal casings.
I've tried disconnecting the kill wire but nothing changes.
Am I missing something here? Any ideas?
Thanks,
Paul

 

[99yam40]

Re: Not your usual "no spark" problem, '87 Yamaha 9.9 , 4 stroke

Did you try grounding both plugs to the block at the same time?
Some motors spark has to go through both plugs , it is called waist spark I believe.

Is there a problem with the way the motor runs?

 

[pemmink]

Re: Not your usual "no spark" problem, '87 Yamaha 9.9 , 4 stroke

Yes, I tried grounding both plugs - no spark.
If either plug is grounded - no spark.
If neither plug is grounded and held several inched apart - no spark.
They will only spark if not grounded and held close enough together so that a spark can jump between the casings.
The motor would not start, so I started troubleshooting the ignition.

 

[pemmink]

Re: Not your usual "no spark" problem, '87 Yamaha 9.9 , 4 stroke

OK, problem solved, or so it seems.
I think both plugs were shorted. I sprayed them with some carb cleaner and blew them out with air.
Now they spark when grounded.
That was wierd...
Thanks 99yam40 for your suggestions

 

[99yam40]

Re: Not your usual "no spark" problem, '87 Yamaha 9.9 , 4 stroke

Probably just flooded.

 

[robert graham]

Re: Not your usual "no spark" problem, '87 Yamaha 9.9 , 4 stroke

You can't always tell a plug is fouled just by looking at it. Carb cleaner, an old toothbrush and an air hose works pretty good, most of the time...