7.3 IDI Turbo Starter Issue

Need some help diagnosing a starter issue on my new-to-me truck. I’m trying to avoid throwing more parts at it.

Truck:

• 1994 F250 XLT 4x4
• 7.3 IDI Factory Turbo
• E4OD automatic

Issue:
Truck needed glow plugs. I replaced them and after the second start the original starter seemed to fail. The original starter would still crank/start the truck, but it made a horrible loud rattling noise that almost sounded like a spun bearing.

I replaced:

• Starter (Cost Less Auto Parts, part # VI 17037)
• Fender-mounted starter solenoid/relay

Problem now:
The truck starts immediately and cranks fine, but the starter does not disengage from the flexplate after startup. It stays engaged while the engine is running and makes an extremely loud rattling/grinding noise underneath the truck. After shutting the truck off, I hear a “wheeeeeering” / spin-down sound like the starter finally releases.

Important diagnostics already done:

• I unplugged the trigger wire while the truck was running and the starter still stayed engaged.
• I’ve tried two different brand new starters thinking the one I got was bunk, and they both did the exact same thing.
• Fender solenoid has been replaced twice.
• Solenoid wiring appears correct, I think.
• Reused OEM starter bolts.
• Starter sits flush to mounting surface, no spacer.
• Flexplate/ring gear teeth are not missing or severely damaged. Minor wear/chipping on some tooth edges but nothing major.

Trying to figure out if I’m chasing the wrong starter, a mechanical engagement issue, or something weird with the flexplate/ring gear. Any help appreciated.

I’m betting you have one wire on the wrong side of your fender mounted relay. Go get a wiring diagram and triple check everything, chasing every wire back to where it’s supposed to be going.

Lastly, I’m guessing you are in Clark County Washington as I think that’s the only place Cost Less AutoParts exists (small world: I used to live in Salmon Creek). Fill out your profile with your approximate location and details of your truck. If some other PNW member sees you are local, they might be inclined to drive over and to a provide you a side by side comparison.

Good luck.