first off i have a 95 chevy blazer 4.3 4wd so heres the problem when i turn the key to the on position it cranks itself over and does not stop until put into gear thus grinding the starter im thinking its the ignition switch is there a way to test it or has anyone else had this problem

 

get under ur dash, find the starter wire, find the main power wire, turn the key to the "run" position, tap a jumper wire to the two and disconnect when its started. that way the starter portion and the switch are tested. if it keeps up then i would check the starter silenoid. otherwise the switch. and you can add a push button switch between the jumper wire as a temp switch fix until u get a new one.

use the pink, white, or brown ignition wires for your power source as the are only on with the key and the starter is the yellow wire for that year blazer.