starter stay on after i pull the key out. if i disconnect the battery starter will stop. if i connect back the battery starter will srart again

Is everything normal with the key in the ignition? Do you have an automatic or manual transmission? Look in the fuse/relay box under the hood. There should be a start relay inside the box. Pull the start relay and see if the starter stops, it probably will. That doesn't mean the relay is bad. You will need to check the input voltages to the relay to find what is keeping the relay closed with the ignition key out. I don't have a wiring diagram for your truck, you will need one, otherwise you are guessing at the problem. Possible sources are, clutch switch if manual tranny, park/neutral switch if auto tranny, ignition switch, the start relay and the wiring harness. I'm sure there are other possibilities. Have any wiring modifications been done recently?

Clifton