1992 Oldsmobile 88 How do you know if starter is bad

Thank you for the information.

I did what you ask me to do. I took out the starter and took it to Pep Boys to have it checked. The starter checked out OK, it was good. The original problem was that the speedometer needle would let's say be at the speed limit, 60 miles per hr. Then all of the sudden, the needle would go from showing 60, to 0, and the speedometer would just stop working, stop registering. Then a little while later, it would start working again, but the car would be hesitating, jumping, and bucking, and then the needle would go back to 0, not registering. I replaced the speed sensor with a used one from the salvage yard. Once I replaced it, I haven't been able to start the car. When I turn the ignition, it just turns but doesn't start. That's when I thought it might be a problem with the started, but like I said earlier, the started checked out good. I'm not sure why the car won't start now.