cdi box

I have read some postings about jumping a jetski frying the cdi. Is this caused by the rapid drop in the rpm of the motor when it hits the water at wot or is this just net-bs?
I am trying to troubleshoot a ski and the testing procedure says to substitute a known good cdi to test. This sounds like a shadetree operation at best since the same thing that fried the first one could easily do it to the "known good" unit.
Does anyone know anything about this subject? I have used an ohm meter on it but the results are iffy at best.
Please excuse me if jetski posts are considered bad manners in this forum.

 

Not bad manners at all, we're all here to muck about on the water.

Could you give a little more detail about what the CDI box is and what it does? do you have a circuit diagram?

Cheers,

Tim B.

 

The cdi is the heart of the electrical system. It controls the spark timing, the charging circuit, the stop engine signal, it limits the rpm's and maybe a couple of other things.
I do not have a circuit diagram for the actual cdi.
There is a pulse coil under the flywheel that sends a signal voltage to the cdi which tells it when to fire the plugs. There is also a charging or lighting coil also under the flywheel that sends a voltage to charge the battery. The cdi does not have a regulator but there is one included in the electronic box for that purpose which is connected to the cdi also.
This is about the extent of my knowledge of the component.
This problem is somewhat mysterious, as the ski was running fine then the engine kill button was pressed with the engine at high rpm. After this action the engine has not fired again. There is a signal voltage from the pulser to the cdi but the plug will not fire at all.
I am far from an electronic expert and only a fair mechanic but if you have any other specific questions needed to help analyze this problem please ask and I will try my best to answer.
Thanks for any and all help.

The kill button is not sticking.

 

test with the ohm meter for currant across the kill swicth to ensure that it's good also disconnect the kill wires at the cd box and see if you have spark
a cd ignition on a ski is the same as an outboard just a differant package i've worked on them both
there are some test to do around the cd box but first you need a peak reading adapter for your meter
test the pulse coil voltage coming into the cd box
then the lighting coil voltage
these test will tell you if the coils under the flywheel are good
the if you have no spark at all it's most likely your cd box to test the output of the cd box you'll need a high voltage shunt (200 ohm resistor)
but to ensure full testing before replacing ohm your coils and wires
this sound simple but it works in the field

 

The stop switch ohms good.
The pulse coil is showing 3.24 volts.
The charging coil is showing 28.3 volts.
I do not have the high voltage shunt you mentioned.
The coil primary ohms at .1 or less.
I don't know how to ohm the secondary since the plug wires are sealed in the coil end.
From this information would you suspect the cdi?

 

yes i would

 

Thanks for the replys. I guess no one knows about the part of my question regarding the jumping? Or what causes the failure of the cdi?

 

Jumping is not the cause. All them Jet Ski's are built for it.

Something got loose on the jump, like a cable connector.
Or some wire was cut by some part of the Jet ski coming down on it like a Guillatine, or was grounded.

It's possible your Control unit is not dead, just cannot function because one of its 'Terms' are grounded.

CDI in my old brain is Capacitve Discharge Igniton. I think you probably are talking about a Computer they may be calling a Control Distribution sumpinorother.

At any rate, if I'm understanding you correctly, someone depressed the kill switch and it never worked again.
I'd suspect that kill switch. Disconnect it from the CDI and see if it will start.

If your CDI is bulit in such a way, you may be able to disconnect everything except the Ignition and see if it will start.

Excuse me if I'm leading you down the garden path here. I've never so much as touched a jet ski.

 

Well, I finally determined it was the voltage regulator. The only thing I had not checked.