help with starting problem

I need help with my Toyota 4runner i try to start it but it won't start all i get is a weak turn of the engine.so i jupm it and it starts i let it run for about 10 min and then turn off the car and try to start it again but i still get a weak turn.i checked if it was the alternator by disconnecting the negative post on the battery while the car was still running.correct me if i'm wrong but thats one way to ckeck if your alternator is bad right? anyways does anyone have any suggestions for me.

Check your battery ground to the block and other connections.