Re: jump starter
You run a wire from the battery side of the solenoid to the small post on the side. make you you connect to the + side, the other one is wired to ground.
I use battery cables to bench test a starter.( Connect to a good battery, ground the black and touch the red to the post on the starter)
I would check for voltage on the supply side of the solenoid first(from battery). you should have 12 volts on the battery side and nothing on the other until you hit the key. then it should read 12 volts as well. If not check the little hot wire in the solenoid for power from key switch> This will get you off on the right foot to find the problem>