Hey there, Vette friends.

I have just spent the last 8 months restoring the front and rear suspension, differential, brakes, bearings and revitalizing the engine bay, including a new water pump and radiator on my 1978 L82 Pace Car (350 with 350 Turbo tranny). I took copious notes and pictures as I was removing parts and have placed everything back as originally noted and photographed. I went to start it up, but it will not crank. I have dome lights, radio and headlights. I took the year-old battery back to Autozone (Duralast Gold (800CCA)), but they said it was good and had plenty of cranking power. I made sure all the new ground strap I installed (from block to frame) has clean pure metal sruface to make contact. I took voltage measurements at the starter and found 12.6 at the main (+) terminal. However, the "s" terminal was getting nearly no voltage when key was moved to "start" (0.5V). I screwdriver tested the starter and it started cranking.

Problem #1: Starter
It is the orginal ACDelco starter. When I jump-tested the starter, it started cranking, but never stopped after I pulled the screwdriver off the S terminal. I had to run and detach the battery posts. I then pulled it off the car and bench-tested it using the same battery. It worked perfectly after a couple of trials (pinion out and spinning). I put the starter back onto the Vette and tried again with normal key start. Nothing. So, any clue why the starter would stay running even after I pulled the screwdriver away?

Problem #2: Potential bad ignition switch
So, I chased the voltage up the purple wire from the S terminal. I checked/cleaned the wiring harness contacts at the firewall. All good. The fuseable links at that connection both had nearly 12V (depending upon when I was testing as the battery was keeping the cabin lights on all the while i was diagnosing for hours. The purple wire had only between 1 and 0.5V when I would "start" the car. I tested the NSS to find the same voltage at both purple and yellow wires. I then checked the yellow wire at the ignition switch above the steering column. It was a max of 1.0V upon start. I ordered a new Wells fuse from Amazon. However, I am not 100% sure that is the issue either.

Any advice would be very appreciated..

 

Remove purple wire from S terminal on solenoid. Now test Voltage when turning key to start. You say you unfortunately have a automatic transmission, (so sorry). Have you checked voltage before and after neutral safety switch?

 

I will remove the purple wire this morning and test both the terminal and the wire as you requested. I tested voltage before and after the Nuetral Safety Switch (NSS) yesterday. While turning the key to "start", it produced only 0.5V. Therefore, I pulled down the steering column and checked voltage while trying to start the car and got about 0.5V. I'm thinking its a bad ignition switch. However, which wire supplies the ignition switch with power to send down the yellow wire after the key is turned?

 

Here are 2 drawings for your 78...

 

And in combination with above you can also get a wiring diagram from Papawana by writing him, believe he needs your email address. The diagrams are great to keep on file. !:
https://www.corvetteforum.com/forums...nyone-248.html

 

Thank you for the diagrams. I will be replacing the ignition switch today and let you all know.

 

 

So, I finally figured it out. The ignition switch had gone bad. Further, I found that that the ignition switch had to be adjiusted to match the key cylinder. All is working now. Thank you for all the help. A few more tests and fluid changes and I will have all the suspension and differential finished.

 

Glad you got it going!
Now, if you would have followed the 1978 passenger car service manual instructions the job would have gone much smother.
This manual along with the assembly manual are must have manuals.
Example of the 78 Passenger Car Service Manual:
https://www.ebay.com/itm/15632652130...Bk9SR5Cpiu3PZA