[CR427NJ]

I installed a rebuilt 351w in my Cobra and had it running briefly a couple of times but yesterday the battery got weak so I put the charger on it. Charger kept cycling on and off so I removed positive cable and connected charger directly to positive terminal. After charging for a few hours I went to put cable back and I am getting constant power to starter as soon as I put the cable on tight. I checked all over for a short but can find nothing. Could a solenoid gone bad cause this? It was a new one. After turning the air blue I gave up. Any ideas?