Starter Problem

can anyone tell me about the purple wire to the start at the bulk head the purple wire spits one goes to the ignition switch and the other goes up into the dash some were were does it conect to? The problem i am having is when I start the truck the start energizes and stay on even when I turn the key off. ( STARTER SPINNING) I've change the starter twice and the ignition twice as well i cant find what is giving power to the starter I disconnect the srtart as it is doing it and it still spins what is going on also i can find any diagram that show any other components withing the starting system help anyone:bloated: 1989 suburban 2500 2 wheel drive 454 engine

I believe I am having the same problem with my 99 Tahoe. When I am driving the starter will engage, then I have to turn the car off then start it in Neutral. I have burned 1 starter and put the other one in but let me know what the problem is?