Ok well, I have a 97 chevy lumina 3.1 engine. I replaced the starter solenoid after having the starter tested and found out it was a bad solenoid. So when I hooked everything up when I went to hook up the battery the positive cable smoked a little and the starter gets engaged and wouldn't shut off until I unhooked the battery from it. Everything is wired the way it was when I took it off and all the bolt are in the right places so can anyone tell me what possibly would cause the starter to engage as soon as the battery is connected? Keys were out of the car so I know the ignition was not on. Does anyone have a diagram of the wiring to the solenoid so I can verify it is connected correctly? Any help is greatly appreciated!

 

Either the new solenoid is faulty or you are connecting the battery cable to the wrong post on the solenoid.