C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

no spark from the top

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Old Jul 29, 2012 | 03:42 PM
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Default no spark from the top

I decided to open a new thread about my no spark problem.
here what I have done

almost rebuild the distributor. new ignition coil, new pickup coil, new cap and rotor. did not change the module, because i can not get it here in my country.

I change the ecm. becouase the other one was afecting my injectors. but the one I get is an used one . not sure if this one is good. one thing I have to do before instal the new ecm was to change a capacitor, that was broken inside the ecm. I did use the one I had in the old one. so that let me to think. this last ecm is no good.

If I disconect the 4 pin connector on distributor I get a spark but if I re conecte , them i have no spark condition.

my question.
do no spark conditon have something to do with the ecm???????

I read some where that the ecm only take information from distributor to set timing or something.. dont really know
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Old Jul 29, 2012 | 10:42 PM
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You should try to test the ICM.
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Old Jul 30, 2012 | 01:22 AM
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The 4-pin connector on the distributor goes to the ECM. The ECM controls the timing of the spark. Disconnecting the connector will put the ICM in "bypass" mode (the same as opening the EST connector). Your timing will be fixed at the base advance (6 degrees, or whatever you set it to).

Sounds like the "new" ECM has a problem. Did you put the MEMCAL from the old ECM in the new ECM?
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Old Jul 30, 2012 | 10:51 AM
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Originally Posted by Cliff Harris
The 4-pin connector on the distributor goes to the ECM. The ECM controls the timing of the spark. Disconnecting the connector will put the ICM in "bypass" mode (the same as opening the EST connector). Your timing will be fixed at the base advance (6 degrees, or whatever you set it to).

Sounds like the "new" ECM has a problem. Did you put the MEMCAL from the old ECM in the new ECM?
yes i did
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Old Jul 31, 2012 | 01:58 PM
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Have you tried to see if there are any trouble codes stored in ECM ?
Will it at least flash a code 12 to let you know it's communicating ?

I know I keep asking you about stored codes, but I have yet to see any info that you have at least tried.
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Old Aug 1, 2012 | 07:21 PM
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hi agent . i did try to get the codes . bit i get no light on the control dash . so at the momento no way i can get code
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Old Aug 1, 2012 | 10:04 PM
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Where are you looking for this light. It's the SES light on info panel, above radio.
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Old Aug 2, 2012 | 03:23 AM
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There is a troubleshooting section in the FSM that tells you what to do if you have no SES light. Page 6E3-A-18.
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Old Aug 2, 2012 | 10:01 AM
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Originally Posted by AGENT 86
Where are you looking for this light. It's the SES light on info panel, above radio.
my main dash is mo working and the panel on top the radio that how allí the light is disconected
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Old Aug 2, 2012 | 10:05 AM
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Originally Posted by Cliff Harris
There is a troubleshooting section in the FSM that tells you what to do if you have no SES light. Page 6E3-A-18.
ok bit i think the problema is. that the circuit is ola and in bar shape i had it out once and justo by looking at the circuit film yo can twll is bad .
i think i had a pintura some where Will try to post later
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Old Aug 3, 2012 | 02:54 AM
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Pin D on the ALDL connector also connects to the SES light. You should be able to use a test light on that pin after shorting pins A & B together.
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Old Aug 3, 2012 | 09:01 AM
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Originally Posted by Cliff Harris
Pin D on the ALDL connector also connects to the SES light. You should be able to use a test light on that pin after shorting pins A & B together.
This is new to me, where are you getting this info ?


Originally Posted by hitmanpty
my main dash is mo working and the panel on top the radio that how allí the light is disconected
Plug it back in or make a temporary SES light. ECM grounds one side of light socket, other side is fed from injector 1 fuse.
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Old Aug 3, 2012 | 02:07 PM
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I just got the new ecm today . I just plug in and see if I have spark now. IF NOTHING them I know I have to look somewhere alse. since this ecm is tested and warranti
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Old Aug 3, 2012 | 03:47 PM
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Originally Posted by 1986coupe
You should try to test the ICM.


my money is on the module. but, when you change out a capacitor or some other component in an ECM, no one can predict the results.
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Old Aug 4, 2012 | 01:46 AM
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Originally Posted by Cliff Harris
Pin D on the ALDL connector also connects to the SES light. You should be able to use a test light on that pin after shorting pins A & B together.
Originally Posted by AGENT 86
This is new to me, where are you getting this info ?
FSM. Page 6E-5. Figure 3.
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Old Aug 4, 2012 | 08:16 AM
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Originally Posted by Cliff Harris
FSM. Page 6E-5. Figure 3.
That would have to be a GM generic graphic, as I have never seen it in any of the electrical schematics.

Just to be sure, I just went and looked, and no terminal in "D".

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Old Aug 4, 2012 | 02:10 PM
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ok I just instal the new ecm.
now i have spark. ok
I have 40 psi fuel preasure and holding
Injectors wires have pulse when crank

so I have fuel, i have spark and i have good air. dont see no vacum leaks.since i fix them all.

the only think i can think of. is timing.

i did remove the distributor compleately.

but I did the following.

first piston all the way up. at TDC. i check with a metal wire the position of the piston. also in the way up I use my finger to feel the preasure on cilinder number 1. coming up. them use the harmonic to move have ench to put on tdc mark.

alight the rotor to point to number one cilinder and instal the new dist. pole cap, number one alight with rotor.

treaple check the fireing order on spark plug wires.

I get no start situation. not even an explotion.

one think call my atention. the spark I notes kind of weak spark. dont have a point of referance. but look to me like the spark is weak.

but remeber I have new pickup coil, new ignition coil cap and rotor

can someone point me to the right direction. like to have this solve this week end. I know I have to be close.

Last edited by hitmanpty; Aug 4, 2012 at 02:14 PM.
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Old Aug 4, 2012 | 03:38 PM
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I just when down to the car again to check the spark.

and is very weak. is small spark is color yellow and is very thin.

I think is suposto be blue and strong

I think the timing most be ok. since I did set up everything the best way I know.

please someone advice
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Old Aug 4, 2012 | 03:47 PM
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When you changed coil, did you remember to fasten the ground strap to one of the 4 coil mounting screws ?
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Old Aug 4, 2012 | 03:57 PM
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Originally Posted by AGENT 86
When you changed coil, did you remember to fasten the ground strap to one of the 4 coil mounting screws ?
yes
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