LT1-LT4 Modifications 1993-97 Gen II Small Block V8

No spark from coil

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Old 05-13-2011, 04:03 PM
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Default No spark from coil

I just got my car back together after having my opti repaired by msd and I now have no spark out of the coil. What wires should I check for power at the ICM and what wire on the coil is supposed to pulse; I trhink it might be a bad ground, one of the ground wires connecting to the back of the coil housing is torn up; it is the black wire, the white wires are fine.
Old 05-13-2011, 04:34 PM
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Replace the coil Less than $20
Old 05-13-2011, 05:06 PM
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A little diagnostic goes further than just throwing parts at it.

http://shbox.com/1/4th_gen_tech2.html#opti_test
Old 05-13-2011, 05:17 PM
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I also had a bad connector and bought one from here works great
http://www.eficonnection.com/eficonn...ngineType.aspx
Old 05-13-2011, 06:16 PM
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I have power at A on the ICM but no power at D on the ICM. What are the possible causes of this
Old 05-13-2011, 08:22 PM
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From the link I posted -

"Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad."
Old 05-13-2011, 08:35 PM
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Originally Posted by henry172
I have power at A on the ICM but no power at D on the ICM. What are the possible causes of this
What the ICM plug on or off? If the plug is on, unplug it and try it. Let us know.

Al 95 Z28
Old 05-13-2011, 09:33 PM
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OK I finally got power going to all of the terminals, but I have a short somewhere. If I unplug the coil there is no short, but as soon as I plug in the coil with the key on the ignition fuse blows. Is this a bad coil
Old 05-13-2011, 10:28 PM
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Got the car to fire up, but it will not run correctly and shuts off. I found that one of the ground wires from the back of the coil housing is no longer ground. There are three ground wires; one is two white wires hooked together, the other is from the side of the frame, and the one I am having a problem with is the black ground wire. The problem is the black wire is now hot when the key is turned on; where is this black wire running to, the PCM?
Old 05-13-2011, 11:56 PM
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Anybody have a diagram showing where that black ground wire runs to; I traced it back to a fuseable link, but that is as far as I got and I did not find where it is getting the power from.
Old 05-14-2011, 01:06 AM
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Does that black wire run down by the starter? I also changed the starter when I did the opti.
Old 05-14-2011, 03:37 PM
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It seems that the black ground wire is ground for the engine sensors; when I pull the fuse for the engine sensors the ground wire no longer has power going through it. What sensors are ran off of the engine sensor fuse under the hood?
Old 05-14-2011, 04:19 PM
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OK I found out what is going on; but now I have a mess of wires to put back. I started thinking that the short had to be only on one ground wire causing all of the wires ground wires to go hot. So at the fuseable link where a bunch of black ground wires are connected I started cutting them one by one until I found the wire with the short; hot wire. I found it and traced it going behind the motor and over the trans. I then thought the only engine sensor back there is the rear O2; so I unplugged it and the ground wire is no longer hot. I am just going to leave it unplugged for now and get all of these darn wires wrapped back up; I should be good to go now.
Old 05-14-2011, 06:09 PM
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No its not fixed I thought I had it but I had all the other sensors unhooked. As soon as I plug in any o2 sensor the black wire goes hot. Anybody have any ideas as to what could cause this? That black wire should be ground.
Old 05-14-2011, 07:46 PM
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I hate this darn car first the opti goes and now I have a short in my engine sensors; most likely the short caused the opti to take a crap out. I want to blow this car up now.
Old 05-15-2011, 01:54 AM
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Originally Posted by henry172
No its not fixed I thought I had it but I had all the other sensors unhooked. As soon as I plug in any o2 sensor the black wire goes hot. Anybody have any ideas as to what could cause this? That black wire should be ground.
You sure it's not the O2 sensor heater?

http://shbox.com/1/HO2S_connector.jpg

Al 95 Z28




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