Here are a couple of links with guidance on the removal of the knob:
How Do I Remove Pull Starter Knob?
1974 W115 240D Pull Start knob - Rebuildable?

I have never done it, so unfortunately I cannot share any 1st hand knowledge. Good luck.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).