Wants to start without the key in it when I put the ground cable on

Welcome to 2CarPros.

I'm not sure what you are saying. The heading says it tries to start without the key in it when you attach the ground cable. The post says it won't start with the key in it, so I'm not sure what is happening.

If the starter engages when you connect the battery (key out), then you are getting power to the s terminal on the starter. That is the smaller wire. That should only get power when the key is in the start position.

Since you just replaced the starter, are you sure the main cable to the starter direct from the battery (thick one) which is hot all the time isn't touching the wire to the s terminal? I attached a picture of the starting system schematic below and highlighted the two terminals I'm referring to. For the starter to engage, the key must be in the start position which sends power through the starter relay to terminal 50. Once it does, a plunger is electrically pulled to the left and the contact plate allows power to flow via terminal 30 to the starter motor, which then turns the engine. So, if the starter is turning with the key out, power is getting to terminal 50. It could be a short at the starter from the repairs.

Let me know what prompted you to replace the starter.

Joe

Can you turn the key to the on position without cranking the engine over to see if you hear the pump in the tank?

Here is a guide that should help:

https://www.2carpros.com/articles/car-cranks-but-wont-start

Please run down this guide and report back.

If it is a remanufactured starter from a parts stores then the starter itself will most likely be defective. I would recommend you exchange the starter and get back to us if it solved the problem or not.

Had a co worker trying to help a friend with s starter and same thing. As soon as he hooked up the ground the engine started cranking. It had an internal short.

This is how I see it in my opinion. If it did not do it before you installed the new part then the new part is defective. You just need to back track.