ignition switch will not turn past on

hi, the ignition switch on my 92 500sl will not turn past on, the shift lever will move , could the ignition cylinder have failed?? if so anyone know how to change one?? thanks sven.
ps. yesterday i completed the instalation of 2 valves 1 camshaft 2 front gears all new chain rails and chain, the car ran perfect, i took it to the car wash, on the next startup the ignition switch would not move past on, i failed to mention that after returning from the car wash i drove the car up on ramps so i could install the moter mount bolts that i had failled to do, in doing so i had to jack the engine up a little to align the bolts, could this have anything to do with my start problem??

My first guess would be the switch itself; they have a safety feature that won't permit them to go past the on position to the start position but once without going all the way back to off...this is to keep you from accidently engaging the starter when the engine is already running.

Have you tried turning it as far as it will go counter-clockwise and then clockwise to the start position?

Don't see any way it could be related to changing the engine mounts...

Travis