Ignition Key wont turn to start

Ignition cylinder goes to on position but not into start postion . whats the cause? It is a 2001 Chevy blazer.

A restriction of some kind. Disassembly will be required to examine.

• Faulty ignition cylinder/ key and tumbler
• Linkage from ignition cylinder to ignition switch
• Ignition switch faulty
• something restricting linkage from ignition cylinder

IGNITION LOCK, REPLACE

1. Remove upper and lower steering column shrouds.
2. Turn ignition lock cylinder to start position.
3. With a suitable awl, insert tip into ignition lock cylinder access hole, Fig. 1.
4. Push down and hold ignition lock cylinder retaining pin.
5. Turn lock cylinder to Run position.
6. Pull lock cylinder away from steering column.
7. Reverse procedure to install.

IGNITION SWITCH, REPLACE

1. Remove steering wheel as outlined under “Steering Wheel, Replace.”
2. On models equipped with tilt column, remove tilt lever.
3. On all models, remove two tapping screws from lower column shroud, then the lower shroud.
4. Remove two Torx head screws from upper shroud.
5. Gently pry retaining clip on key alarm switch with suitable screwdriver, then rotate switch 1/4 turn and remove.
6. Remove Pass Key connector from lock module assembly, Fig. 1.
7. Remove two tapping screws from ignition switch assembly.
8. Remove wiring harness from slot in steering column head assembly.
9. Reverse procedure to install.