TallTim

iTrader: (2)

Ok I am getting frustratingly lost on this one, please see if I am on the right track here.



Per the FSM I followed the green arrow below to the point where I am to "repair the module + term to B term of black ignition coil connector OR

primary circuit to ignition switch.

At the same time looking at

http://easyautodiagnostics.com/gm_ic...n_module_5.php

where it says the ICM connector 1 A terminal (aka the FSM's ICM + terminal) I see I should have 12v at that terminal. But I have 5v on A and zero on B

So I don't see how going by the FSM instructions to repair "module + term to B term of coil" is going to help if I don't have 12v to the ICM.

(even putting 12v directly to it makes no diff so maybe I have 2 probs)

So that takes me to OR part of the FMS instructions "repair the primary circuit to ignition switch"

Can anyone suggest how I "repair the primary circuit to ignition switch?"

Save my sanity on this one please!

Tuned Performance

iTrader: (92)

The first point you would want to check is the voltage at the grey connecter at the coil. If it is below 10v chances are the issue is in c100. If not than the jumper going from the coil to the icm has too much resistance.

TallTim

iTrader: (2)

Thanks for that fast comment...Forgot to mention when I trigger the MSD 6AL by grounding the white wire on it the spark lights right up. Otherwise Key On the grey connector at the coil has exactly zero volts.

TallTim

iTrader: (2)

Tuned - that jumper has 2.5M ohms resistance. Once I get 12v back to the ICM then will a test wire from ICM + to coil + remove that as a source of the prob? Thx.

Tuned Performance

iTrader: (92)

The black connecter jumper since it is short I would suspect 1-1.5 ohms would be the max you would get. Tbi car and truck jumpers are the Same but you will need to extend the wires bye splicing in a piece. I'm assuming your ohm meter is in the correct setting. IIRC the msd 6al white wire is hooked into the icm/ coil negative trigger wire. Did the loss of spark happen when you started to hook up the 6al or just random no spark ?

TallTim

iTrader: (2)

Here is the evidence that is taking me on this troubleshooting mission.



Strangely car was running fine until I stumbled on this. I have replaced dist, cap, and rotor, sp and sp wires (others were old). I'm testing for spark at the coil with a spark tester.

Ok so let me get some clarity on what you say

1. The jumper being short is not obvious to me between coil + and ICM + because in my stock harness the coil + goes into one harness and the ICM + goes into another. But a jumper would just go between the two right?

2. I have a DVM so I set it on ohms and it reads from 0 to infinite by itself.

3. I am going to separate C100 and see if there is any melting or what. I have not found any wires or insulation melted so far and no codes thrown.

Regarding codes though, when I jumper AB the DS rad fan comes on. Wierd?

Thx for your guidance.

Tuned Performance

iTrader: (92)

No problem found here looks normal, lmao It is normal for the ecm to command the fans on when the ecm is in field service mode.

1) just guessing your using a msd part 8876. The power from to the icm splits off of that adapter on the orange and black wire. If you are running a msd distributor you can use a gm icm, the cheap Chinese icms are junk. The pu can be replaced separately and are just soldered to the icm.

TallTim

iTrader: (2)

Tuned thanks for mentioning the 8876. That caused me to familiarize myself with it (PO installed it) and document how it is wired in. I was curious why the orange and black wire went to the IAT under the plenum instead of the dist. Doh! Identical connectors and almost the same length of wires caused me to reverse the connections. Besides that the C100 looks fine and I tightened the DS head ground wires at the back of the head which were only finger tight. Will post more when I've got a moment to see if spark returns! Thx again.

TallTim

iTrader: (2)

Oh re: that burned cap and I'm thinking either 1. The springed nib in the cap touching the rotor fell off causing huge arcing and heat between the cap and rotor or 2. Something was telling the coil to spark way more than it should have causing over heat and arcing as the rotor was sometimes near a plug terminal sometimes not.

TallTim

iTrader: (2)

Update - I switched the IAT and the dist 2 pin connectors to their correct locations and the spark returned. Thanks for the troubleshooting help Tuned.