CDI Help!

yamy · 12-13-2009, 12:09 PM

I'm trying to troubleshoot my G1 which died yesterday. It has no spark at the plug when I turn it over. There is no voltage in the orange wire which is going into the ignition coil, so I don't think the coil is the problem. This orange wire comes from the CDI unit, which I'm not sure what that is. I'm assuming it regulates the spark and I know it is expensive (over $300). So how can I verify that the CDI unit is working? There is voltage coming out of the magneto's brown wire, which goes into the CDI unit.

Thanks ahead,
Tom

smallblock450sl · 12-13-2009, 01:48 PM

Quote:

Originally Posted by yamy

I'm trying to troubleshoot my G1 which died yesterday. It has no spark at the plug when I turn it over. There is no voltage in the orange wire which is going into the ignition coil, so I don't think the coil is the problem. This orange wire comes from the CDI unit, which I'm not sure what that is. I'm assuming it regulates the spark and I know it is expensive (over $300). So how can I verify that the CDI unit is working? There is voltage coming out of the magneto's brown wire, which goes into the CDI unit.

Thanks ahead,
Tom

Sounds like you've check out enough to beleive it's the CDI. Do you know anyone else with a G1, all the CDI's are the same ,so you could test it with a known good one. 300.00 seems high for a CDI. Try to place a "want to buy" post in the "for sale" thread. Good luck Dave

GMB74 · 12-13-2009, 02:10 PM

I wouldn't rush into replacing the CDI unit just yet. That would be last on my list of possibilities. Most likely you have a loose/corroded connection or chafed wire. Look close at the four connectors coming out of the engine. Check your harness where it comes around the battery and exhaust. Look in the stickies section above for a wiring diagram if you don't already have one. Do you have an ohmmeter to check for continuity and resistance?

smallblock450sl · 12-13-2009, 02:22 PM

Quote:

Originally Posted by GMB74

I wouldn't rush into replacing the CDI unit just yet. That would be last on my list of possibilities. Most likely you have a loose/corroded connection or chafed wire. Look close at the four connectors coming out of the engine. Check your harness where it comes around the battery and exhaust. Look in the stickies section above for a wiring diagram if you don't already have one. Do you have an ohmmeter to check for continuity and resistance?

Did I say to buy a CDI? Apparently he knows how to use a volt meter. I assumed he checked the connections from his well tought out post.

GMB74 · 12-13-2009, 02:35 PM

I'm not trying to start a battle here, just trying to help the OP. Since there is no way to test a CDI control unit short of replacing it with a known good unit,it is prudent to check everything else thoroughly. If he is satisfied with his diagnosis, then your suggestion to post a "want to buy" is very good advice.

yamy · 12-13-2009, 07:30 PM

Thanks for the reply guys. I'll check the wires again as I really don't want to replace the CDI, and I don't have access to another one for testing purposes. I have a wiring diagram.
To bad CDIs are difficult to test. I would like to verify the magneto is working as this seems to feed the CDI. Does anyone know how to test the magneto?

skarp · 12-13-2009, 08:29 PM

I just had the same problem....no spark and nothing coming out of the coil!!!

It ended up being the group of wires that run along the battery box....seem to have shorted against the frame.

Moved them and fired right up.

Hope that helps!!!

Stephen

GMB74 · 12-13-2009, 09:13 PM

Pulser coil resistance 14 ohms (white/red wire to white/green wire)
Charge coil resistance 370 ohms (brown wire to black wire)
Test these wires on the engine side where they come out of the engine. The black wire is a ground and should have continuity to ground. On the harness side,the other 3 should not have continuity to ground (shorted wire as skarp found) but should have continuity to the CDI control unit connector. Open circuit= broken wire in harness. Unplug the control unit during testing to prevent letting the Magic Smoke out of the box!

kogieblack · 12-26-2009, 10:05 AM

Just check your ground.

yamy · 12-27-2009, 11:28 AM

UPDATE:

I missed testing the ohms between the spark plug lead and the ignition black wire (ground). There is zero continuity there, and it should be 5900 ohms, right? Anyway, since my spark plug lead has cracks in it and the boot is torn up, I ordered a new ignition coil. I'll update what happens when that arrives. I think I'll also order the service manual which hopefully has all the ohm specs for testing.

Thanks for the help!
Tom

12-13-2009, 12:09 PM	#1
yamy Not Yet Wild Join Date: Sep 2008 Location: Melbourne, FL Posts: 32	CDI Help! I'm trying to troubleshoot my G1 which died yesterday. It has no spark at the plug when I turn it over. There is no voltage in the orange wire which is going into the ignition coil, so I don't think the coil is the problem. This orange wire comes from the CDI unit, which I'm not sure what that is. I'm assuming it regulates the spark and I know it is expensive (over $300). So how can I verify that the CDI unit is working? There is voltage coming out of the magneto's brown wire, which goes into the CDI unit. Thanks ahead, Tom

12-13-2009, 02:10 PM	#3
GMB74 Gone Wild Join Date: Jun 2009 Location: Heluvabump,VT Posts: 623	Re: CDI Help! I wouldn't rush into replacing the CDI unit just yet. That would be last on my list of possibilities. Most likely you have a loose/corroded connection or chafed wire. Look close at the four connectors coming out of the engine. Check your harness where it comes around the battery and exhaust. Look in the stickies section above for a wiring diagram if you don't already have one. Do you have an ohmmeter to check for continuity and resistance?

12-13-2009, 02:35 PM	#5
GMB74 Gone Wild Join Date: Jun 2009 Location: Heluvabump,VT Posts: 623	Re: CDI Help! I'm not trying to start a battle here, just trying to help the OP. Since there is no way to test a CDI control unit short of replacing it with a known good unit,it is prudent to check everything else thoroughly. If he is satisfied with his diagnosis, then your suggestion to post a "want to buy" is very good advice.

12-13-2009, 07:30 PM	#6
yamy Not Yet Wild Join Date: Sep 2008 Location: Melbourne, FL Posts: 32	Re: CDI Help! Thanks for the reply guys. I'll check the wires again as I really don't want to replace the CDI, and I don't have access to another one for testing purposes. I have a wiring diagram. To bad CDIs are difficult to test. I would like to verify the magneto is working as this seems to feed the CDI. Does anyone know how to test the magneto?

12-13-2009, 08:29 PM	#7
skarp Gone Wild Join Date: Nov 2009 Posts: 250	Re: CDI Help! I just had the same problem....no spark and nothing coming out of the coil!!! It ended up being the group of wires that run along the battery box....seem to have shorted against the frame. Moved them and fired right up. Hope that helps!!! Stephen
skarp Gone Wild Join Date: Nov 2009 Posts: 250

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12-13-2009, 09:13 PM	#8
GMB74 Gone Wild Join Date: Jun 2009 Location: Heluvabump,VT Posts: 623	Re: CDI Help! Pulser coil resistance 14 ohms (white/red wire to white/green wire) Charge coil resistance 370 ohms (brown wire to black wire) Test these wires on the engine side where they come out of the engine. The black wire is a ground and should have continuity to ground. On the harness side,the other 3 should not have continuity to ground (shorted wire as skarp found) but should have continuity to the CDI control unit connector. Open circuit= broken wire in harness. Unplug the control unit during testing to prevent letting the Magic Smoke out of the box!

12-26-2009, 10:05 AM	#9
kogieblack Gone Wild Join Date: Apr 2009 Location: Vegas NV Posts: 262	Re: CDI Help! Just check your ground.

12-27-2009, 11:28 AM	#10
yamy Not Yet Wild Join Date: Sep 2008 Location: Melbourne, FL Posts: 32	Re: CDI Help! UPDATE: I missed testing the ohms between the spark plug lead and the ignition black wire (ground). There is zero continuity there, and it should be 5900 ohms, right? Anyway, since my spark plug lead has cracks in it and the boot is torn up, I ordered a new ignition coil. I'll update what happens when that arrives. I think I'll also order the service manual which hopefully has all the ohm specs for testing. Thanks for the help! Tom

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