Crazy Starter Activity!?

[SlimTheGreat]

Recently purchased 08 Grand Prix w/3800 motor, while driving home starter engaged by itself. I pulled over immediately shut the car off waited a retried to start the car. The starter engaged in the ignition on position not start position! (!!) I continued to restart and the engine struggled to start but eventually did long enough to get it home. Looking over the car the original starter & solenoid looked terrible!(like it was smacked wit a hammer more than a few times).Checked the engine compartment fuse panel and heard a soft buzzing sound from the crank relay even with the key off. Tried swapping relays with new one, still does the crazy activity.Purchased/Installed a new starter & solenoid but the problem continued, purchased/installed a new ignition switch same problem continues.(!!) My next move is replace the ECM but it's pricey. Now I'm lost any Ideas where to go next before replacing the ECM. Thanks in advance for you input and advise!

[Scottydoggs]

almost sounds like the starter's not wired right.

maybe take it out leave the wires hooked up and see if its works off the car, you'll need to ground the starter when its unbolted, jumper cable to the nut on the back with a thick wire to to the solenoid on the starter then to the neg post on the battery will ground it. watch the little Bendix gear to see what its doing. when grounded, and key turned to start. and back to run.

it should stay in the nose cone until you hit start, then it should pop back in when you let the key go back to run.

some times they pop out hit the flex plate and stick there. they let out this nasty whine when its stuck on the flex plate when its running.

then theres also the chance of a damaged wire somewhere causing a bridge in power, someone with a ohm meter and the knowledge how to use one could pin point this rather fast i'd think.

[SlimTheGreat]

I've only tried loosening the starter and using jumper cables to hotwire the starter. I'll try your suggestion and let you know how it turns out

[SJAndrew]

My gtp starter would engage by itself. It was a simple short circuit at the starter solenoid with unswitched positive terminal shorting against switched stud on starter. Loosened, reassembled with heat shrink and it's been fixed since.

[02NavyBlue]

On GM RWD vans we've had 3 come in already with the same issue, starter self-engages on it's own in the run position. It will shut off in drive and reverse, but shift into neutral or park and it grinds away. Turns out that the issue was in the neutral safety switch as it contains many circuits, and it was shorting internally feeding power to the starter. A new one fixed all 3 vans/trucks, but was difficult to replace because the connectors were melted to the switch. I can't say for sure that's what's causing your issue, but something's powering up the starter when it shouldn't be. Does it stop grinding in drive or reverse?