Im posting this question for my dad. He has a 2001 4x4 blazer that has recently been having problems starting. When the key is turned on all of the dash lights etc come on, but nothing happens when it is turned over, no click, no turning over. Occasionally it will start after several attempts, and then runs fine. But sometimes it will take 15-20 minutes of trying before it will start. He has checked all of the fuses and relays and they are all good. He replaced the ignition switch (the wiring harness under the dash, not the lock cylinder) and it worked fine right after that for a few hours then it stopped working again. If anyone could help with the problem I would really appreciate it.

 

I'd begin by testing the main power & solenoid trigger wire for +12v at the starter when the key is turned to the 'start' position. If the small solenoid trigger wire on the starter isn't getting +12V, I would check the 'crank' fuse in the underhood fuse/relay center. If that is good, test the crank wire in the large connector under the steering column (details on which wire that is can be found in the ignition switch link in my signature below).

 

I had this problem in my 2000 Olds Bravada and after spending over $100 in parts it ended up just being the battery cable. I replaced it and cleaned the contact point on the battery and it started every time.