I'm reduced to just brainstorming now without seeing the thing in front of me. All I have to go on is the exploded view of the steering column (see attached).
Does the ignition switch operate correctly through all its positions including ACCESSORY?
I assume the rack gear that operates the switch and the sector gear on the lock cylinder have never been disassembled to where the teeth mesh incorrectly (gears out of time with each other)?
Did the mechanic say what was wrong with the rack gear? If some teeth are chewed up on the end, the rack may not be able to drive the slider in the switch all the way to START position. Can you watch the rod push the slider along in the switch as lock cylinder goes from LOCK to START? If motion stops after it goes through RUN, then rod travel is insufficient to make the START contact close. With lock cylinder held in START position, can you drive the actuator rod (#76 in pix) farther by hand and make it start up?
The wiring can be cleared if it is possible to start it up by working the slider in the switch with a rod or screwdriver. Have to be extremely careful doing this test to not let the starter stay engaged if engine starts up. Be ready to pull fuse 1A in a hurry if something hangs up.
While off the column, the slot in the slider can be checked to make sure it is not chewed up or damaged.
Last edited by TODD; 10-12-2017 at 03:34 AM.
What has been, can be again. (Bob Wills, 1942)