How can you tell if a starter is bad on the car?

[WH23G3G]

I tried to jump that old Datsun with a new fully charger 300 AMP jump pack and my daily driver Ranger and they both made no difference in starting? All the lights work and everything works with ACC power on, and when you turn the key you can hear some kinda of click, and it will try to turn the motor once, but barely. I probed the battery with a multimeter and it showed 12.3 before trying to start it and then 11.2 after I tried to start it. I also disconnected the negative cable and probed the negative terminal with a test light and it didn't light up at all. So that means there is no shorts right? Is there a way to test the starter to see if its bad? I remember when I got my Charger the guy had to strike the relay on the firewall with a screwdriver to get it to fire up. On this Datsun it's mounted to the starter. Can I do this trick on a starter like that?

[4aThrill]

yes, you can do that, if your starter is easy to take out, you can also take your jumper cables to it to to see if the cog gets pushes out and spins. it's pretty fun. hook the + to the starter of course then the ground near by but don't touch them to together.

[Back N Black]

There is a couple of simple things that you can try before you pull the starter.It could be a bad engine to body ground, take the negative side of your booster cables and attach one end to a good ground on the engine and the other end of the cable to a good ground on the body, crank it over see what happens?
It also could be a bad starter ground, take your test light and ground it to the body and touch the test light on the starter casing see if it lights up.
if it does run a ground wire from the body to the starter casing and try to start it.
Last but not least do a starter draw test with your multimeter.
Hope this helps