94 LT1 cranks but no start
07-15-2018, 12:36 PM
#1
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94 LT1 cranks but no start
Looking for ideas why my engine won't start. I traced that I have no spark at the plug wires or coil. Took the ICM to Autozone to have tested and it checked out good. Took a DVM and checked the connector to the ICM with the key in the on position and found I have 12.68 volts to both terminals A and D. Checked AC voltage to terminal B while cranking the engine and have 3 volts. Probed terminal C with a test light and that was good. Threw a new coil on it and it still will not start. Is there some other testing I could do to figure out why the old girl won't spark and start? Could it be the optispark? got me stumped. Any suggestions would be greatly appreciated.
07-15-2018, 03:35 PM
#2
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Re: 94 LT1 cranks but no start
If you have the AC volts on pin B, the PCM is receiving the cam position signals from the Opti. If the ICM tested “good”, and you do not have spark, the next suspect is the coil, and you indicated no spark at the coil wire. But you replaced that.
Screening test for coil - read the note to be aware this is just a continuity test:
Courtesy of Shoebox
http://shbox.com/1/coil_testing.jpg
If you had spark at the coil wire, and not at the plugs, the next in line is the Opti. Not unheard of for the rotor screw(s) to fall out.
Have you scanned the PCM for codes?
While you are focused on spark, have you checked the fuel pressure?
Screening test for coil - read the note to be aware this is just a continuity test:
Courtesy of Shoebox
http://shbox.com/1/coil_testing.jpg
If you had spark at the coil wire, and not at the plugs, the next in line is the Opti. Not unheard of for the rotor screw(s) to fall out.
Have you scanned the PCM for codes?
While you are focused on spark, have you checked the fuel pressure?
07-21-2018, 12:36 PM
#3
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Re: 94 LT1 cranks but no start
Fred thanks for the feedback. I checked the fuel pressure at the Schroeder valve and have 42 psi. I tried connecting my innova 3140 scan tool to read the codes but am getting a communication error so I'm not sure if the reader works with this car. It's a 94 Z28. LT1 A4. I have done some mods. Hot cam kit, erg delete, air delete, headers, throttle body.
07-21-2018, 03:34 PM
#4
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
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Re: 94 LT1 cranks but no start
I know there is a problem with the Innova 3120 (and the equivalent Equus model) with regard to the OBD-1 LT1. The scanner’s stored data base for the LT1 codes is corrupt and returns a list of 8 bogus codes when it finally connects. Whether that defect carries over to the 3140, I don't know.
Scan9495 data logging software is the best available. Free download:
https://www.camaroz28.com/forums/com...95-lt1-874306/
And, the author is here to help with install/setup issues, if any.
Scan9495 data logging software is the best available. Free download:
https://www.camaroz28.com/forums/com...95-lt1-874306/
And, the author is here to help with install/setup issues, if any.
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