Starter spins, does not engage flywheel

[Larryjb]

The problem with the new starter is definitely the solenoid. I'm not sure if the spring it too strong or the solenoid is not strong enough.

The problem with the old starter is probably that it all the contacts need cleaning, needs new brushes, new bushings, etc. Also, I suspect the solenoid spring is too weak or broken.

 

[Larryjb]

I just bench tested the ACDelco Professional new starter and the pinion gear does not extend all the way out.

 

[dictum]

I have an identical problem. It will start after about 2 attempts. Do I replace the flywheel? The start is new.