starter work fine on bench, does not work in car?

I have a 355 starter that ...:

1) tested just fine on the bench: connects 12V to big terminal, Ground to body of starter, jump 12 volts to small terminal (Ignition) and bendix gear jumps out, and starter spins.
2) Install starter in the car, connect 12V to large terminal, ground to body of engine at the starter, connect 12V to the small terminal: Starter motor does spin but the engine does not spin because the bendix gear does not engage with ring gear. So, I cannot perform a compression test.

Why?

 

Bad ground/contact
Not enough juice in the battery to drive the bendix gear
Bad alignment/blockage
Bad bendix gear/solenoid

 

Yeah...I agree. Jump the starter directly with known good battery power to make sure the problem isn't the car electronics. Make sure you in neutral and chocked.

Sometimes bad solenoid the pecker will pop out but have no chutzpah!

 

It's the clutch in the Bendix gear. New starter is needed. It cannot be rebuilt.

 

Your starter bench-tests fine but won’t engage the flywheel in the car most likely due to voltage drop under load or a weak solenoid signal. Check battery health, clean all connections (especially the small trigger wire), and verify proper ground. If voltage stays strong but it still won’t engage, the starter might need a shim or the solenoid is failing under real-world load. A compression test requires solid cranking, so fix this first.