1974 W115 240D Pull Start knob - Is it Rebuildable? It won't always start by pulling all the way out, a over-ride button was in place when I got the car. If the pull start doesn't work, most of the time the buton does - (one wire goes from button switch to batt and other to starter)

But I would like to know if there is some sort of contact on this rod that it makes contact with, can it be rebuilt and/or fixed? I'd rather have it start like it was originally designed to.

Also, sometimes I get a dead spot where it won't do a thing, neither button or the pull, playing with the key switch most times gets it started. So do I have two faulty switches or just one and can the pull knob starter be rebuilt/fixed?

The Knob will shut down engine and it will activate the glow plugs

Is there a specific manual for this model year of car without getting a Chilton or Haynes manual which is so bland?
Also same for the 240D 123 chassis?