Yamaha 40 Ignition help needed

[bever]

1985 40 HP Yamaha. After hours of searching the threads I havta ask for help. I'm experienced with CDI ign trouble shooting but here's my dilemma. Engine will hard start but runs on # 2 only. Removed all spark plugs for spark test and only # 2 has strong blue spark. #1 & #3 will spark only once when the key is initially turned to start, after that one spark it's no show. I swapped the coil supply wires to see if I could "move" the spark and sure enough the good spark follows the #2 input wire (trigger, pulse whatever it's called) from the Black Box. So the Coils appear to be good. Next was the OHM Resist test. I tested all three wires from the Black Box to the coils and all 3 had exact same readings. Same test from the black box to the stator wires and all three wires had same reading. Could it be an alarm circuit or some other system telling the ign. to limit fire to only #2.
Any feed back on this is greatly welcome.

 

[aussie_mike2]

Re: Yamaha 40 Ignition help needed

Hi , sorry I cant help you with you problem , just curious have you fixed the problem.

I have a similar problem with a Yamaha 90 HP outboard 2-stroke motor where cylinder 3 is not firing the spark plug.

Since I'm not familiar with the ignition system on outboards, I trying to find information on ignition systems for that vintage of motor and hopefully I will be able to fix mine.

Cheers

 

[rodbolt]

Re: Yamaha 40 Ignition help needed

ok
that engine uses a single charge coil to charge the capacitors in the CDI unit,hence the term, capacitor discharge ignition.
funny how that works .
your sparking on one so most likly the charge coil is ok but you need to test the output voltage cranking and loaded(system hooked up normally) brown to blue you should see about 200V peak.
test CANNOT be done with a standard meter you MUST use a DVA adapter or the correct peak reading style meter.
RMS is NOT peak.
then on to the pulser coils,you have 3.
each triggers its respective cylinder.
w\r is 1,w\b is 2 and w\g is 3.
cranking loaded you should see about 2V peak minimum.
also try disconnecting the white kill wire from the CDI, this will eliminate the kill circuits.
your CDI output to the ign coils should be about what the charge coil input voltage is.