Is starter working?
 

I just rebuilt my engine using your books and wanted to test the starter before I put the engine and transmission back in the car.

I jumpstarted the starter attached to the engine using my battery and starter cables, and the starter operates but the engine does not turn.

I tested to remove the starter and jump started it again on my workbench. The motor is running and the gear is turning, but the gear does not extend.. so I assume that is why it does not engage with the flywheel teeth.

Is it a problem with the starter or is it just the way i jumpstart it? I grounded it and connected the + cable to the terminal closest to the starter, not the battery connection that usually is connected which require the ignition switch.

I have. 911 SC 1980.

Best,
Daniel

Did you jump the relay?

No.

There are two major terminals, the battery + connector and the one close to the starter connected to the field winding with a strap. Also, we have the flat connectors to the ignition switch (top) and the cold start injector (bottom).

I connected the battery + to the terminal connected directly to the starter field winding, bypassing the relay.

Is there another (proper) way to jump it?

your relay is there to pull then bendix out to the teeth on the flywheel.
bypassing that -your starter will just spin freely

Many thanks, works great now.

Solenoid........
 

You meant solenoid instead of relay?

Tony