Please help, no spark but CDI and coil seem O.K. By looker (Read 5,013 times)

[looker]

Hi guys,
scooter ran fine yesterday, (gy6 qmi152) warmed it up then dropped it off the main stand and it cut out. Cranked over fine but would'nt start back up. Fuel is getting through and I can smell gas through the tail pipe.
Pulled the plug and checked for spark, there is'nt one!
Changed out CDI and coil, still won't start.
Did a continuity check on the black/white wire to the CDI, o.k. Turned on ignition and still have continuity, turned kill switch to 'not run' and same thing.
What could cause the continuity to stay the same with the ignition turned on? Faulty ignition switch?

I'm gonna now check the switch and do some other tests like the stator and other wiring, kill switch, side stand kill switch wiring (though that switch was removed a long time ago)

Could there be other things to look for?
As it happened when I pushed off the stand I'm thinking the impact has dislodged something somewhere.

Any help will be greatly appreciated, I really need to get it running,
cheers guys,
Mike

[looker]

Tested stator, 133 vAC from red/black wire, 1 vAC from blue yellow wire.
Unplugged ignition switch and have continuity from black/white wire. turn switch on and the circuit is broken. With it plugged into the harness there is continuity with with the key in the on and off position.
Unplugged kill switch on handlebar, no circuit in the 'run' position, continuity in the 'not run' position.

I guess that leaves me stripping down the harness and tracing the black/white wire to see if it's shorted somewhere

Mike.

Forgot to add, all lights and controls work. The funny thing I noticed this morning when first trying to start it again is the 2 lights on the instrument cluster that flash with the direction indicators came on briefly!

[tvnacman]

is the engine ground good

[sprocket]

This may help. It sounds like ignition switch or kill switch

Attachments:

[looker]

Hi guys,
engine ground is fine

sprocket,
that's what I thought. Here goes with the rest of todays shinanigans.
Sitting comfortably?
I stripped all the panels off back to the frame and took the floor board off so I could easily get to the harness. Exposed the black/white wire all the way from the kill switch right upto the CDI. No evidence of any shorts anywhere on any wires!
Kill switch appears to work as it should, open or closed.
Ignition switch appears to work as it should when disconnected.
Again tried the spare CDI that I have and still getting the same continuity problem. Then I thought, and this is the real killer, unplug the black/white wire from the CDI and try the probe on the side where it plugs into the CDI.
No problem with continuity, turn off the ignition switch and the circuit is broken
Looks like I have 2 bad CDI's. What are the odds
If only I had thought of checking with it unplugged in the first place, I would'nt have a scoot in bits with an unwrapped harness Live and learn I suppose.
So after all that it now looks like I do need a new CDI.
I'll order one and hope that will be the cure.

Cheers guys,
Mike

[sprocket]

Try this... pull the black and white wire from the CDI. This wire is shorted to ground by the kill switch and the shorting stops the engine.

So, if the kill switch is deceased, and maybe internally shorted, then the CDI both of them are always in a grounded state. No engine working...

Much more likely a bad kill switch than 2 CDIs... so if the black & white wire is good, it has to be the kill switch...

You need to test the kill switch to see if it is actually functioning, ideally with a meter to see if it is grounding on the kill and not grounding on the run postion

[buford1488]

i pulled all my hair out going through that once and only to find out the kick stand switch was the issue....buford..

[buford1488]

with you saying about the lights flashing i would suspect a bad ground like tvnacman said..

[looker]

Buford,
kickstand switch is long gone, removed it a long time ago so as not to have any problems from it.

Sprocket,
when you say test the kill switch, how do you mean? I removed the switch and used a circuit tester and it works as a switch should, contact or no contact.
If the switch is removed, is it not as though the switch is there and in the 'run' position. When the switch is on the scoot and in the 'not run' position it's basically joining the 2 wires on the back of it together creating the ground?
If the ignition switch and/or kill switch were bad, would I not get the same reading from a circuit test if the black/white wire was connected or disconnected from the CDI (if that makes sense?)

Electric circuits give me a head ache trying to figure them out

Got a new CDI coming, will most likely only know for sure once that is here.

Thanks guys,

Mike

Nearly forgot, if there was a bad ground somewhere would that not cause other problems? like head lights going dim when the brake lever is pulled. I had everything turned on, lights, emergency flashers, brake light....and when I pressed the horn button no lights dimmed or anything!
The 2 green arrow lights on the instrument cluster has me stumped, they've never done that before or since!!
Got me thinking now, I took the muffs of the handle bars today and the left one is very close to the emergency flasher switch, maybe it was too close and had the switch in an almost on position.

[sprocket]

The way the kill switch works is , it simply makes a connection between the B&W wire and ground. This shorts the CDI and kills the engine...

It does not matter if the B&W wire was connected to the CDI or not as long as the switch is open (no ground). Often these switches fail in the closed position, so as long as the B&W wire is attached to the CDI the engine will not run...

That is why I suggested removing the wire from the CDI, in the event that it was always closed. (grounded)

[looker]

Ahhh, sorry Sprocket, I mis-read your post. I think I see what you are saying now, no black/white wire on the CDI.

So if it still won't start, then it must be the CDI?

If it does start, how do I turn it off ;D

Cheers, I'll try that in the morning.

Can the CDI itself be tested in any way?

Mike

[sprocket]

Yup you got it... Hopefully it will run without the B&W attached to the CDI. To turn the engine off, simply run a wire from the frame (ground) and touch it to the CDI where the B&W wire should attach...the engine will stop.

Then you know the problem IS the kill switch

The CDIs can be tested, but only the voltage coming into the CDI from the stator and pick-up coil and the outgoing voltage on the black and yellow going to the coil. It could be very high voltage...

[tvnacman]

a bad engine ground will give you the same sysmptom

[looker]

tvnacman,
engine ground is fine and dandy and now the harness is exposed I can see the wire is in great shape too. I also think I replaced the ring connector on it a while ago as the original looked a bit 'weak'.

sprocket,
I'll try your suggestions today.
To be honest, I'm hoping it's the CDI as everything else I've tested appears to be functioning as it should. I'll wrap the harness back up today as I don't think there are any wiring problems, do a few more tests and then wait for the new CDI to come.
The other (spare, original) CDI has been rattling around in the under seat bucket since July last year. Maybe it's had a rough time and won't work anymore. The one that's on the scoot now is an orange/red Bando, I bought it in the hope it would be a better stronger constructed piece of kit!

I've seen a CDI in a few places online, usually gold or blue in colour with the connector on the end of a short harness and heat sink fins molded into the case. Wondered if anyone has used this type and what it's like?

Thanks for all the help guys, especially sprocket, being able to talk it out has given me the understanding to try and test what needs to be done.

I'll let you know how it goes if I get the thing running!!

Mike

[looker]

wrapped the loom all back up nice and tidy, connected all the plugs back onto where they should go and then thought, give it a try, the damn thing started up
Worked with both CDI's.
I then went around pulling and twisting all the connections, banging the ignition switch, pulling on the harness, even gave the whole scoot a good shaking!! just carried on running!

Only thing I found, there was a quiet 'ticking' noise now and then when moving the wires near the CDI, pulled the rubber boot off the coil and moved the wires again. There was arcing on the spade connector of the black and yellow wire.
Closed the spades up a bit with pliers so they fit tight and the arcing stopped.

I don't get it, I tried a different coil previously with no luck.

All I can think is, it was that coil connection, the kill switch is on it's way out (have a new one coming) or the ignition switch is on it's way out.

When I do a continuity test on the black/white wire with the connector plugged into the CDI (I only have a 'dial' tester, not a buzzer type) the needle moves slightly when I turn on the ignition. If I unplug the blk/wht from the CDI and do it again the needle drops to 'no circuit' when I turn on the ignition!

Gonna finish putting the last couple of panels on tomorrow and go for a ride on local roads and not stray too far from home. It's really bugging me now because I hav'nt fund a definitive cause.

Mike