replaced starter/engaging without key

HELP - We replaced the starter in our 99 tahoe but when we reconnect the negative battery cable the starter engages without the key - it started the engine on it's own. Any ideas or suggestions?? This is the second re-man starter in just a few hours. Connection is correct.

Are you saying the engine actually started or was just turning over constantly? If it's just turning constantly you may have a faulty starter relay that does not disengage. Check for 12 volts at the small wire on the starter which would indicate a stuck relay. Replace the relay. If your engine actually runs without a key you have serious wiring problems.

make sure battary cable is not tuching soliniod wire when you instaled the starter,it is commen mistake

Check the connections, If it is starting when you connect the batt. you have power getting to the starter. I gurantee you have crushed a wire or have 2 wires touching. Check it out, I know it can be frustrating.