Dva voltage bouncing around

toddingalls · Jul 11, 2012

Received my DVA adapter today.
Tried to test some components on my yamaha outboard. (1990 115hp 2stroke v4)
The meter/DVA doesn't seem to hold the signal long enough to get an accurate reading.
I had it set on 200v DC with the DVA plugged in.
Mostly all I could see was voltages bouncing around... couln't get any accurate readings.
Am I missing something?
Thanks
Todd

99yam40 · Jul 12, 2012

Re: Dva voltage bouncing around

maybe it is a defective device, where did you get it from?

There is a bleed off resistor in it to discharge the capacitor, but it should not drop voltage fast.
Should allow voltage to build up.

I would call who you purchased it from

toddingalls · Jul 12, 2012

Re: Dva voltage bouncing around

Got it through ebay. Sent him a message last night about returning it.
Just to confirm.... the correct setting is 200v DC with the DVA plugged in?

99yam40 · Jul 12, 2012

Re: Dva voltage bouncing around

depends on what your measuring, but if it is the charge coils or CDI out put that should work
here is a drawing of what one is made of

toddingalls · Jul 25, 2012

Re: Dva voltage bouncing around

Follow up post.
#4 cylinder output from the cdi is showing only 95v testing with a dva meter.
1st question: Does this mean bad cdi? Supposed to be 125v minimum.
I have no spark on #4.
Stator and trigger test ok as far as ohms and peak dva volts.
Replaced cdi about 5 months ago.
2nd question: I am wondering what could be causing cdi to go bad, any ideas?
Pricey part to keep replacing!

99yam40 · Jul 26, 2012

Re: Dva voltage bouncing around

was the testing done with CDI still hooked to coil?
What did you get on the other 3?
Did you come up with a different DVA?

Seems like I remember reading something about bad coil could cause voltage spikes feeding back into CDI and damaging them

Try checking ohms on coils

toddingalls · Jul 26, 2012

Re: Dva voltage bouncing around

Testing was done with everything still hooked up to CDI, including stator, trigger, and ignition coils. Is that not correct?
Also do I need to test CDI at different RPM's? Or just turning it over with DVA connected?
I have no spark at all RPM's on #4, so I was testing only while turning motor over.
Other 3 CDI outputs tested around 155v.
New DVA meter.
I swapped out the ignition coil on #4, still no spark. I will test ohms on ignition coils.

toddingalls · Jul 27, 2012

Re: Dva voltage bouncing around

Any help?

99yam40 · Jul 27, 2012

Re: Dva voltage bouncing around

need to find out if coil or wiring is dragging down the voltage to #4.
might try measuring with it disconnected, I think manual calls for that too
Check plug cap and secondary wire also

toddingalls · Jul 28, 2012

Re: Dva voltage bouncing around

Thanks for the reply.
Follow up: Disconnected #4 ignition coil and had similar result with the DVA meter, less than the minimum 125v on #4 CDI output. Only showing about 55v. So.... does it seem like a bad CDI?

99yam40 · Jul 28, 2012

Re: Dva voltage bouncing around

if all inputs to CDI are good then it would seem the CDI is bad if the output does not meet spec

toddingalls · Jul 28, 2012

Re: Dva voltage bouncing around

Thank you for your reply.
Ordered CDI... Ouch.
Hard to wait for the part. How bad is it for the motor to run on 3 out of 4 cylinders for a few hours? Might create some build up of unburned fuel/oil in #4 cyl?
Thinking about taking the boat out for a while just on real light duty.

toddingalls · Aug 9, 2012

Re: Dva voltage bouncing around

Follow up post:
Diagnosis was correct. I Changed out the CDI and she's firing on all cylinders now. Running good.
If anyone has any ideas how to prevent blowing out CDI units please reply...

Dva voltage bouncing around

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