Fixing an 89 iroc z 5.0 for my friends husband, as a surprise from when he gets back from deployment. The only thing I know about the car is that it wouldn't start/ had some battery drainage issue. He replaced the battery, starter, and alternator. I got to looking, and he had the ignition wire to the starter on the wrong post(the R post for coil power). Moved it to the S post, and the car started right up. Only problem is the starter keeps engaging...Even after you take the key out, it's still cranking on the flexplate.

For troubleshooting, I decided to check ignition wire first. I disconnected power from the starter, and put a Voltmeter lead on the ignition wire( that goes to S post). Turned the key to start, 12V, back to run, 0V. All looked well there, so I looked to the starter. Got it tested at O'reilley's and it was fine. Read some forums, and figured it could be that the pinion wasn't retracting due to clearance problems, keeping the starting circuit engaged. Installed a sh*t ton of shims, but the problem still exists.

So back to wiring, decided to monitor the S post on the starter while it was hooked up/ energized. Key to start, 12V, engine starts. Release key to run, starter keeps running and Voltmeter reads 9, 8, then 7V constant. Thats not right! Why would the ignition read differently on the first tests when it wasn't actually engaging the starter, than it is now?

I'm assuming now that the problem actually is the ignition. Am I thinking along the right lines? Is there any remote possibility that it really is the starter? Where/ how should I begin testing the ignition, because I cant keep the starter constantly starting to recreate the issue- for fear of burning it out/draining battery.

 

 

Update:
Finally got around to continue troubleshooting, and I found the problem completely by accident. I planned to simplify troubleshooting and bypass the entire ignition/enable system by running a wire directly from the battery to the solenoid start post. while making final measurements, the wire accidently made contact with the positive battery terminal(ignition was off, mind you), and the starter cranked... and continued after being startled and ripping the wire completely off . Again, with only the power wire attached to the solenoid, starter is continuing to crank. With that, undisputable evidence that the solenoid is bad and failing to cut power to the starter motor. I immediately ran to the parts store for a new starter, dropped it in, and now works perfectly.

Moral of the story: Don't trust the part store's testing machine to detect all possible issues. Caused me much frustration and unnecessary work.
Happy troubleshooting everyone!

 

Finally got around to continue troubleshooting, and I found the problem completely by accident. I planned to simplify troubleshooting and bypass the entire ignition/enable system by running a wire directly from the battery to the solenoid start post. while making final measurements, the wire accidently made contact with the positive battery terminal(ignition was off, mind you), and the starter cranked... and continued after me being startled and ripping the wire completely off . To reiterate, with only the power wire attached to the solenoid, starter is continuing to crank. With that, undisputable evidence that the solenoid is bad and failing to cut power to the starter motor. I immediately ran to the parts store for a new starter, dropped it in, and now works perfectly.

Moral of the story: Don't trust the part store's testing machine to detect all possible issues. Caused me much frustration and unnecessary work.
Happy troubleshooting Y'all!
Starting system wiring diagram