BF8A From Hell no spark

"About six months ago I "

"About six months ago I "shotgunned" an intermittent no start/no spark BF8A by replacing the cdi unit and ignition coil. The complaint was that after running and shutting down, the motor would not re-start. This motor is back - and after running for about five minutes, it stalled and would not re-start. A spark tester showed no spark - even after several hours of cool down. The neutral switch tests ok. The kill switch tests ok. The cdi charge coil tests at 268 ohms and shows a clipped, or rectified ac signal peaking at +54 volts cranking. The cam sensor (or pulser coil) tests at 126 ohms and scopes a consistent ac signal +1 volt to -1 volt during cranking. The still fairly new ignition coil primary is .57 ohms and secondary is 26.5 k-ohms. The cdi unit will rarely deliver any substantial signal to the ignition coil primary.

Replacing the cdi unit (again) brought instant, but short lived results. After running for five minutes - dead...no spark.

The seloc on-line manual that I bought is no more useful than an owners manual. NO comprehensive specs for the cdi charging coil and no test procedure for the cdi unit. Also, no technical description of the cdi module logic with regard to the oil light circuit. i.e. if the light is burned out, will the motor start; and if so, for how long? I could see that if the neutral switch is opened or the kill switch closed, cdi charge voltage is zero while cranking.

Does anybody know what kind of waveforms & data are to be expected from the charge coil and pulser coil? Any ideas on what could be killing the cdi output to the ignition primary? Could there be a mismatched ignition coil? I have part numbers, serial number and can forward a snapshot of coil waveforms."

"That is a lot of diagnosis. T

"That is a lot of diagnosis. The only thing that comes close to you problem is one I had on a 15 hp.

I literally replaced every ignition component on a rental motor ( I had several to work with) and nothing would make it run longer than 15 min.

It turned out to be the cam shaft.--- Ya I couldn't believe it either. The ignition ran like bat doo and when the new cam was installed, It went like new again. So just on a dare-- look at the lobes on the cam shaft."

I was wondering if a new cam s

I was wondering if a new cam shaft worked for you? Having the same problem with a BF75.

"The cam shaft sounds interest

"The cam shaft sounds interesting, but it seems that you will still get spark as long as you are getting the voltages that you are indicating. The timing would be messed up and the engine may not run, but there should be some sort of spark. I have found the easiest way to check spark is with a timing light on the plug wires. I seem to have troubles with spark testers on hondas due to the small spark compared to the "lightning" that you get from Evinrudes.

I assume you continue to have the outputs that you stated when it fails. I also assume that you can measure voltage at the coil primary when it is running and you do not when it is not running. It sounds like you are using a scope to measure voltages. Generally the coil gets about a !00v peak to peak ac when cranking. That is consistant with your scope measurements. The only numbers I have been able to get from Honda are running values. Not much help when cranking.

Make sure all the the ground connections are good and if they ground at different points on the engine, jumper between them to assure a good common ground.

This is going to sound crazy, but you did not say whether the oil pressure light was working or not working. It is not needed for the engine to run. Disconnect it! Leave that circuit open. If for some reason the light is shorted internally or drawing too much current, it will send a hard ground directly into the power pack and the result will be the same as activating the stop switch. I have had one that had a bad light and the motor would not run at all. It surprised us all!

I am also assuming that you have disconnected the stop switch already. If you haven't, disconnect it. To take the neutral safety switch out the circuit you have to bypass it or short across it. They may test good but still look like enough of a short to stop the engine after it is heated up.

One other possiblity... If you are getting voltage to the coil all the time, you may have a bad spark plug. The secondary circuit is a series circuit of the coil secondary through one spark plug through ground to the other spark plug and back to the coil. A cracked spark plug can open when it is hot and open the circuit resulting in no spark."

"My problem with the 15 showed

"My problem with the 15 showed only on the timing light and only after warm up. It did effect all the cylinders and eventually shut down the ignition. I have no explaination. The exact same ignition went on another motor and ran fine all season. Honda is famous for it's "goofy" electrical designs. I have a 79 ten horse with points and the points goes to the coil, the exciter coil goes to the coil, the oil light goes to the coil, the coil has one post yet it all works!!! My only logical way I figured it worked was with what would amount to a positive ground??

So back to your problem- yes the bad cam can kill the ignition. And it's easy to spot- one or more of the valves just barely opens. Will not show up on a compression test."

The OP wrote.. "...The cdi

The OP wrote.. "...The cdi charge coil tests at 268 ohms..."

Honda Shop Manual Spec for this is 330 ohms (+/-10%) and a new one that I installed many years ago tested 360 ohms out of the box or +9%.

You might run a jumper wire to

You might run a jumper wire to ground the trigger (at the cam)to the CDI(bracket) and the engine case(near the oil light) to the coil bracket(on the engine block)????? Disconnect the kill and neutral switch.(hook together).

Pilotart soundes like he may have something there with that low ohms reading also. But you might test your ohms meter aginst a known number before spending that kind of money. Wouldn't buy a $200.00(?) part on the say so of a $15.00 meter.

"Agree on confirming before bu

"Agree on confirming before buying. Mike above mentioned 100 Volts and OP was seeing 54 Volts as well.

I paid $79 for the flywheel ignition coil in 2005 from my- local Honda Dealer, they are gone now.

[url=""]http://www.boats.net/parts/search/Honda/Outboard Engine/parts.html[/url]

Has it listed for $65 (new OEM Honda part).

I agree with ground checks, especially the primary coil. The CDI has a ground wire and the pulsar trigger coil is a closed loop to the CDI.

I saved replacing my CDI (nearly $200) when I found several rotten core copper wires from CDI (one was to the neutral switch)."

Re: "several rotten core c

Re: "several rotten core copper wires "
This is caused by using (cheap) copper wire with a high owygen content. Copper wire with a high oxygen content can literally turn to powder (I've seen it happen) in a marine environment.
Checking and replacing those wires (use good qualty marine wire) may be a good step.

"^^^^^^^^^^^^^ [img][/img] [im

"^^^^^^^^^^^^^ These were in the harness of the original Honda 'CDI' unit.

20% of the length of the leads turned to brown paste and the REAL cheap stuff turns to green powder,
all the way to the end.

Big problem is that the continuity is not instantly lost with this deterioration,
but it initally causes an intermittent problem.

Nothing more difficult to chase than an intermittent problem which is well hidden within the insulation."

"The phenonom of corrosion in

"The phenonom of corrosion in copper wire (especially at elevated temps) with high oxygen content was well known as far back as 1960.
Unfortunatly the way things are structured in Japan, that CD unit was probably not made by Honda, but rather by which ever company MIDI decided was the designated marine electrical component manufacturer in Japan."

Thank you all who responded -

Thank you all who responded - just replace the pulser coil and exciter coil. Spark is back and motor running great. So much for bench testing!!