No offense to bluelightnin6, but wanted to correct the information in this post, as it is incorrect. I just went through the same problem, and found this page while researching.
The problem in this case is NOT the ignition lock cylinder. The lock cylinder does not contain any springs. The problem IS the ignition switch. On a 2000 (what I own also), the switch is in a full harness, and plugs into the bottom of the lock cylinder housing (the part the cylinder fits into). The actual electric starter switch has an internal spring that is attached to the plastic gear at the top of the switch with a brass pin. When I removed mine, I could see where the gear was broken, which created the exact same symptom Silverado Simpleton described.
If you do it yourself, the cost of a switch is about $100, and takes about an hour. You don't have to pull the steering wheel, just remove the upper and lower steering column covers and lower trim panel and knee bolster.
I want to help anyone who pulls their hair out on this problem like I did!
Friday, April 1st, 2011 AT 7:51 PM