That red stop lever should be the direct mechanical link to the fuel shut off... not something which activates something else which requires vacuum to work... so yes, I think an adjustment of that is in order... that IS the emergency , if nothing else works, shut off..
I have looked at my 616 FSM but can not find exactly that information..

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html