Once again you measured on test one: 510,000 ohms (well it was actually 509,000 ohms last time). Half a million ohms! I don't believe it . This is because you also measured 47.8 volts AC with the CDI unplugged, and 28 volts AC when the CDI is plugged in. Both those values sound reasonable, and cannot posiibly be produced from something with a source impedance of half a million ohms. It just can't...

We either need to focus on this *very* wrong answer, or get past it by refuting such an unlikely reading, and after more careful measurement replacing it with a more reasonable value like 510 ohms (not 510,000 ohms). Or at least some set of readings that are physically possible... .

What worries me is that you have described really weird symptoms (and which I or anyone else have not been able to think of any reason that could cause this). Then you repeat twice over readings that just simply cannot possibly be...

It's time to reset, back up and revisit these readings with a fresh mind. Something is drastically wrong with the previous data. If any one of your measurements are suspect then all of them are suspect.

Let's nail down these descrepancies and go from there...

If you really have half a million ohms resistance in your AC ignition power winding then we need to figure out why you are reading an impossibly high AC voltage from the same source.

It's also a two way street... I'm also wondring if *I'm* the one in a mental rut, and the problem is something obvious that I have overlooked. It's possible. I'll be thinking too... . But I've come up with nothing so far...

 

I am sorry for delayed response or wrong info, i have been jumping around this project to much. The reading was actuall .510k ohms.

 

Take a good look at your wiring harness for any loose connections. This is a very wierd problem! It's the only thing I can think of!

 

Good. So we don't need to focus in on that. 0.510K ohms is 510 ohms.

0.054 volts AC at the trigger pin is really low. Was this measured while you were having no spark? You measured 142 millivolts before. Were you having spark at this time?

Your problem is really strange. I'm looking for clues. What are the differences in the meter readings between when the quad starts, when it has weak spark and doesn't start, and when it has no spark at all...

 

Yes that was measured with no spark this time. I am goimg to try a performance cdi I got today. Is there any way that a bad voltage regulator could interfere or back feed to effect my voltage at the cdi. Avout thde only thing havnt done yet.

 

No. Regulators have nothing to do with spark. This is especially true on AC powered ignition systems (like yours) where the entire ignition system is self contained running off AC power coming from the engine. Once the engine is running you could disconnect and remove your battery, and regulator, and the engine would keep on running.

This is why they have two separate switch sections in the ignition switch. When you turn off the ignition switch it removes 12 volt power to everything. But this won't stop the engine. A second switch shorts the kill input to the CDI to ground in order to prevent spark (killing the engine).

Let us know about the new performance CDI results. After that the only thing consistent so far is the trigger voltage being low. Perhaps we should concentrate there. Not being familiar with your quad specifically, can you easilly measure the gap between the trigger pickup coil and the raised bump on the flywheel?

 

OK. Sounds stupid, but a shot in the dark. Is it possible the starter is not spinning fast enough. I noticed the ac voltage was increased with spark if i cranked it over with a drill. about 55VAC. still doesnt explain how heating the cdi would help. But i did get it to fire up and run. Took the starter apart and found a screw was living in the back of the case. cleaned and reasembled with a jump and full charge on the battery, and no difference. New connections from battery back to starter,and i tried jumping starter directly to no avail. My eyes are starting cross and overlook things i think. Going to try a new battery and see. BTW there is no way for me to messure the pickup coil.

 

Yes... Definitely the starter spinning too slow will cause problems. The main concern is the trigger voltage. But lets back up a bit...

The voltage generated on a coil of wire in a changing magnetic field is proportional to the rate of change of magnetic field. The magnetic field is coming from the flywheel, so the voltage in any of the 3 stator windings (unloaded) is directly related to cranking speed. It's called Faraday Induction in case you want to look it up. Of course many other things are involved too such as number of turns, strength of the magnets, gap between magnets and coils, permeability of the core material - but none of these things change.

The battery charge winding we don't care about since it has nothing to do with spark. The AC ignition power winding will produce lower voltage with decreased cranking speeds, but this will produce weaker and weaker spark - not "no spark". The trigger winding is a common theme here. It always reads low. And the trigger voltage is an "all or nothing" event. Either the voltage is enough to trigger the CDI, or it isn't. So you were able to start the quad by spinning the engine faster? And it ran? This all points to the the trigger coil. Remember that once the engine starts it is idling at 1800 RPM, compared to a cranking speed of 600 RPM.

You can't measure the clearance between the trigger coil and the raised bump on the flywheel. I presume this is because the flywheel is mounted to the crankshaft, and the coils are in the engine side cover?

Low trigger voltage is caused by a bad pickup coil, a too large gap between the coil end and the flywheel raised bump, and/or magnetic debris accumulating on the magnet enf protruding out of the pickup coil.

Heating the CDI will cause *very* slight changes in the threshold voltage that the CDI must see in order to trigger. This seems a long shot to me, but I can't think of any other reason for the CDI output to be heat related, as well as engine cranking speed related.

One more test that might be worth trying - if you have the skills to make this:



When you plug this across your trigger wire to ground at the CDI (with the CDI connected or disconnected), both LED's should flash. If they do you can eliminate the trigger signal as the problem.

 

Hi there, I followed your steps for 5 pin cdi, I have 0ohms ac to ground pins, your step 1. Obviously I have a no spark issue. I have another less important problem, to start go cart I have to step on brake and turn key for it to crank, awhile before I lost spark it started cranking with ignition on and foot on brake, didn't have to ever turn key. Can't tell if it stops cranking but assume it doesn't since it spins by a chain and not a bendix type. Doubt they are related but I thought I would give you whole story. Thank you in advance. Btw, I hate this damn gocart. Gimme a Briggs with a cyntrifical clutch and a pull start any day lol!!!

 

Help cdi unit dropping voltage when i crank motor