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ignition circuity

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Old Jul 29, 2021 | 06:52 AM
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From: Stuart, Fl
Default ignition circuity

I have had what seems to be recurring ignition circuity issues during the restoration of my 81'. On several occasions, I get no power to the starter when attempting to start the vehicle.
Two were related to brake or clutch switch.
This week, after reinstalling the center console, same issue.
The only thing I can think of is the plug under the console that has a purple wire, two purple/white wires, and a black wire. The plug seems to be an end point and it is not connected to any other wires. I'm wondering if that could be the problem as it is the only thing under the console I can think of and I know the purple wires are ignition related. I have triple checked and plugged/unplugged the connection. I'm wondering now if I can bypass the circuit to isolate if this is the issue. Else, I'm back to square one. I did however confirm that brake and clutch switch were operating properly.
Any suggestions? What am I missing?
Thanks,
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Old Jul 29, 2021 | 09:18 AM
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PPL is for theft deterrent relay. It is probably this circuit you have problem with. I will attach a schematic if that will help, I am sure there are writeups on this in forum Good Luck
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Chevy Corvette 1981.pdf (269.9 KB, 163 views)
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Old Jul 29, 2021 | 09:56 AM
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Originally Posted by henrikse
PPL is for theft deterrent relay. It is probably this circuit you have problem with. I will attach a schematic if that will help, I am sure there are writeups on this in forum Good Luck
Nice! There's a relay in the 80, and full-up "Theft Deterrent Control Module" in the 81.

I had my relay in my 80 nearly strand me once. Turning it off and turning it back on again fixed it (disconnecting and reconnecting the battery). The relay issue seemed to be related to the order of operation of unlocking the door. When the passenger door was opened first, I couldn't start the car without power cycling it. I unlocked the driver door, and haven't had a problem since. I don't know if the module works the same way for the 81, but at least you have somewhere to start.

Great find @henrikse!
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Old Jul 30, 2021 | 01:14 PM
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St. Jude Donor '15
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Connect ppl/w and ppl to bypass the relay
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Old Jul 31, 2021 | 07:06 AM
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From: Stuart, Fl
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Thank you for the schematic. I had one but have been scratching my head on where to start. I will focus on the PPL/theft deterrent relay. I will see if I can find where the relay is located and go from there. Also, since I did not have a starter issue prior to putting the center console back in place, It is likely the problem is in that area and the terminal block is the only thing I am aware in that location. Now I'll get my magnifier and see if I can read this schematic properly. Thanks again.
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Old Jul 31, 2021 | 07:10 AM
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From: Stuart, Fl
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Thanks for the suggestion. Since this terminal block under the console has two PPL/W and one PPL in addition to the black wire, would I want to connect all three in order to bypass? A had already attempted to bypass by connecting the two PPL/W but no success? Also, is this terminal block that I am describing under the console and just forward of the e-brake, actually the relay itself? It seems like an end point connector?
Thanks again.
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