1999 2.5 Auto.

I'm at my wits end with this problem. I've been looking around online quite a bit but can't find anyone that's had a similar issue.

Long story short the original engine decided to spontaneously disassemble itself on my way to work a few months back. So I bought a (same year) parts truck with similar miles and dropped that engine in.

Now I'm having issues. The starter will not disengage. I've pulled the battery terminals while running, checked the wires going to the starter from the battery, checked relays and ignition switch, cleaned contact points, and even put a switch on the signal wire. Nothing. Won't let go of the flex plate.

I have two starters, they bench test fine. One is a cheap reman from AutoZone, the other was on the parts truck. I had a third one (original AutoZone cheap reman) but the teeth on the ring gear destroyed the pinion.

I'm almost wondering if the problem in the mechanical engagement, where maybe the pinion gets wedged somehow, but I don't know. It hasn't chewed up either of the other starters.

 

Is the starter staying running or not disengaing

The smaller round tube on the starter motor is a solenoid/relay combo unit
When 12v is applied to the smaller "S" post it pulls back the solenoid part which pushes out the starter motors gear, when 12v is removed the gear is pulled back by a spring

The large battery positive cable connected to the starter solenoid/relay is on the relay side
When solenoid pulls back and gear is now out, the relay part connects battery positive cable to the Starter Motor and it starts to spin

You can test just the solenoid part by applying 12v and ground, "S" post for 12v and starter's metal case as ground, gear should come out and then go back when 12v or ground is removed, repeat a few times

Between any engine and bell housing is a Block Plate, thin metal plate, this is used to align the starter motor so its not too close or too far away from ring gear/flexplate in this case
Starter motor bolts are just not that accurate for alignment
So did that block plate get put back in?

Should have looked something like this: https://www.therangerstation.com/for...f9-jpeg.66700/

 

Starter stays engaged like a ring/pinion meshing issue or short inside the solenoid. Even when I shut the truck off (and signal wire is disconnected) it stays engaged. The starters both bench tested fine originally but I'll check the newer one again since I have it off.

Also yes the block plate was put back in, but I do remember accidentally bending it a little bit, and having to flatten it out. The dowels still lined it up fine with the bolt holes for the trans though.