No Spark on LT1?

I was all excited last weekend when I finally got to the point that I could try and start the car, and.... nothing. I used a spark tester at the plug and got nothing. Tested the coil secondary output (coil wire to opti) and got 12V. A few 1000 volts shy I am thinking.

This LT1 is out of a '96 Vette. Testing the ignition coil module harness- white wire intermittent 12V (should be from ECM), green 0volts (going to coil, makes sense), pink 12V (ignition feed) and black tested for continuity to ground. With harness hooked into module and disconnected at coil- both pink and green had 12V.

Tested coil next- primary to secondary ohm test on high scale around 8 ohms. primary to primary prongs on low scale read 7-8 ohms. According to the manual this is good and the coil is brand new.

Any ideas on why I am not getting a high voltage output? Thanks for the help.

try the street and performance web site

Opti-Spark equipped??? If so, that's most likely your culprit and was a huge problem with the LT1 equipped F-bodies.

Mary Pozzi

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Originally Posted by mpozzi

Opti-Spark equipped??? If so, that's most likely your culprit and was a huge problem with the LT1 equipped F-bodies.

Mary Pozzi

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I am only getting 12v from the secondary wire to the opti. While the opti might have issues, the spark problem is before it.

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Originally Posted by paul67

try the street and performance web site

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Thought that was an odd reply until I looked at their website :-) They have a great troubleshooting section and I will try the flow chart for LT1 ignition issues.

I have read another post that sounds just like my issue and it turned out to be the coil that was bad. Suppose it would not be the first time I bought a bad part, but have to wait and see.

do you know anyone else with lt1 and see if you can try his coil.But the opti spark is prone to diying without warning ,if the water pump leaks it canget inoi the rear of the dissy

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Originally Posted by paul67

do you know anyone else with lt1 and see if you can try his coil.But the opti spark is prone to diying without warning ,if the water pump leaks it canget inoi the rear of the dissy

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I don't, but I have tested with an extra coil and went through all the troubleshooting points again and also did them for the opti.

Part of the issue is that I am not sure how the signal feeds through the PCM. Does the opti signal the PCM which then provides the ignition control signal to the ignition control module? It seems my ignition control signal is low while cranking, only .6volts AC, but the guide is confusing on this. The four wires to the opti from the PCM test out: 5v DC on A & B, continuity to ground on D and test light from ground to C lights up. This leads me to believe it is the opti, but again I am not sure of the signal source for the PCM and coil.

I really don't want to tear apart the front of the engine, spent $400+ on a new opti and coil only to find out that was not the issue. Does anyone have a good technical understanding of the control circuit? Thanks.

You have pm

I went ahead and bought a new opti and cable and am in the process of getting it put on (having trouble getting that dang pin to line up :-)
The water pump was brand new, but already had weepage so I have decided to go the electric route. Once everything is back together in a week or two I will post if this fixed the problems.

maybe the ICM?

I replaced the opti and that did the trick as far as spark is concerned. Engine actually starting is another matter! Thanks for the help.