:welcome:
Firstly you are wrong to tack your problems on the bottom of an old thred, but we will forgive you for that.
Starter solenoilds are nothing more than a relay, we used to call them starting relays at one time.
As such you need a + & - to trigger the switch to connect the two heavy wires together.
The + & - can be either two wires, which we call a 4 pole
OR a single + wire and get the - through the grounding and that is a 3 pole.
the starter draws a lot of power so eventually the contacts inside the solenoid burn out
You test it is functioning by jumping to the control wire (s).
It should click fairly loudly and you should get 12V at the starter side.
You check the wiring by checking you get 12V at one of the control wires when you turn the switch to start and have continuity to earth on the other wire or solenoid body.
To me it sounds like you have a bad contact and generally it is the ground contact.