no spark - no ac voltage to cdi when plugged in  By  crawdaddy (Read 9,291 times)

Right. Hoping a real pro can chime in and shed some light. New stator will be in soon here as well. If i Replace it and the scoot starts, then I guess its the last thing to always work. 

John, if you were directed at me mine is an 8 pole but do you agree end result voltage can be directly related to resistance. My high resistance could cause the loss of voltage. I ask to learn and better my diagnosis. I usually work on cars and motorcycles, not ac fired scooters.
Here is my thought process so far:
The cdi needs ac voltage at a decent level to charge the capacitors. It needs a trigger to tell the cdi to throw 'power' to the coil. It needs a good ground and it needs the kill wire not to be grounded. I have provided a known good ground, and taken the kill wire out of the system. With no known good values I have shown 50volts ac unloaded and .7 volts ac from the trigger at the stator. I have not verified the pulse on the trigger because honestly I didn't want to hook up the scope but every test I can find says look for at least .5 vac to fire. Might do that with the new stator and the scope. I have known good cdi boxes, known good spark plug, known good spark tester and known good coils. To me the 50 volts is the lowest I have seen but in theory should show some spark. If in fact those 4 things are the only things needed to spark by process of elimination everything is ruled out except the stator in my case. If the stator doesn't work I am going to put everything in a box, tell him to come get it before I set it on fire and not charge him of course

Took yesterday off.....anyway I'll give the long story update. I put in the new stator and still had no spark. Big surprise huh? I sat there thinking and realized we had forgotten a variable. We had good ac voltage with the plug to the cdi unplugged but lost all but nil voltage when we plugged it in. The variable is the plug. I took the pin out of the connector for the power wire from stator to cdi, it looks fine but when I checked continuity it was open...hard to describe and I've never seen it but there is my problem. When I bypass the pin, go straight from power wire to the power pin on the cdi I get a nice fat blue spark. I've gotta find a replacement connector and wire it all back up but I am confident it will start, no reason it shouldn't. I'll give a final update when I do. All this time and work for a .01$ connector pin.

it was hard enough in person. what I don't get is I was getting the same voltage at the end of the plug - it was only when I plugged it in some connection was lost internally.
I'm now thinking of how I could have found it a different way or any sooner. I was just trusting the plug because of the readings at the end of the plug.
anyway, it is all back together and starts every time. thanks for the support folks. hopefully this scooter won't be back for a while.

yes,the connector to the cdi - specifically the power pin female not making good electrical connection to the male cdi pin somehow. When I removed the terminal from the connector block and plugged it straight into the cdi I was still getting the loss of voltage. When I attached the power wire from the stator straight to the cdi pin , no connector by holding it with my hands, I got spark. I replaced the female pin with a different one, put it back in the connector block and it kept getting spark.
I can't say the connector was loose in that it wasn't pulling out of the block by hand but somehow electrons weren't jiving. The male/female were a tight connection when I tried it while taken out of the connector block. Strange huh....

rich-yes, that was exactly it. I've never seen it either in a nice shiny connection with no corrosion. My brother in law happens to be an electrical engineer and i asked him about it. He said something about internal leakage or something.