New starter spins but gear wont move
 

Sounds like an installation issue.

There should be a spade terminal for the wire with the spade connector. You can see it here (just to the left of the two threaded posts):
https://www.rx8club.com/attachments/...s-dscf2321.jpg

Im having a hard time thinking its install error. I instaled the engine and starter the first time and it ran perfectly for over a month. Now iv replaced dtarter 3/4 times this week with new ones thinking i was getting faulty remans. Install is incredibly simple.

With the starter installed nice and tight, the battery terminal bolt securly fastened, and that spade terminal connected the starter will spin but the gear does not slide out. If i put started on bench and connect power to both of those electrical connection points via jumper cables, the starter gear spins AND slides out.

1) cluth interlock switch bad ?
2) main relay?
3) ignition switch?

Today i scanned car snd got a p0336 code. Then I cleared the NVRAM and still nothing. You can hear starter gear spinning but car wont fire. The belt under hood isnt even spinning. I then spun crank pulley to ensure engine wasnt seized. And i tested the clutch sensor and it tested good. Im stumped

If that’s the case then it sounds like the starter solenoid might be bad.

Then it sounds like an install issue. (Can we keep going around in circles?)

Basic explanation for anybody else who doesn't understand starters.
The interface is very simple. The spade terminal is the trigger for the solenoid. The top screw terminal is power from the battery. The bottom terminal transmits power from the solenoid to the starter motor.

The solenoid is triggered when 12V power is applied to the spade connector. This should extend the starter gear and start it spinning. If it only spins, then the plunger isn't extending the gear.

I dont know how else to tell you it is not installers error. Iv swapped these motors 3 timed problem free, i think i can hsndle 2 bolts and 2 connects. A monkey could replace these starters.

Somthing did occur to me today tho. Unfortunatly i cannot test it for next few days due to traveling but i have a theory. With starter installed you can clearly hear the gear turn, but cannot visually see if it comes out to make contact with flywheel. I assume its not becuase you can see the underhood belt not rotating. BUT what if gear is coming out and making contact with the flywheel which in turn is spinning it but the flywheel has become unattached.

My next test will be to remove starter and while looking at flywheel have friend rotate crank pulley to see if engine will rotate along ith flywheel.

Or the starter gear is extending but is no longer securely attached the starter motor. Maybe enough to spin the gear until a load is applied.

Happened to me also. Turned out to be a separated ring gear from the flywheel. The starter spins the engine doesn't.

I removed the starter to check the flywheel. What I found was that the ring gear would move back and forth in the flywheel groove. Not much but enough that the started would not engage.