Hi. You will need to replace the electrical portion of the ignition switch. This is where the 'spring back' is located.
Your goal is to remove the ignition lock assembly.
I will attempt to attach a couple of pictures. Haven't done this in a while.
First picture is not from a 190, but it will assist. Note the copper button on top of the lock shaft. Right of the left tip. This needs to be depressed to remove the lock assembly. You do this by turning the ignition key to first position.
Second picture is the electrical portion of the lock needing replacement. As seen on the left of the picture. It is held in with three screws.
The procedure to remove the lock assembly takes more explanation than I have room here.
I can provide a more detailed instruction of this procedure to you if you send me your email address. In most cases it involves removing the instrument cluster to access the two bolts securing the steering column to the dash. Lowering the column allows more room to extract the lock assembly. I have done this hundreds of times since I sell lock sets on Ebay.
If you wish help(no charge for instruction) send a reminder request to
cdplayer51@pacbell.net
Please refer to your 190 ignition spring back problem.
Thanks
Dan