major problem with my 1980 123 (240D) a few years ago
but I lucked out when the key turned
after leaving the car set for several days

when my 84 126 (300SD) had the same problem
I sat there sweating on a jot afternoon trying to turn the key
memories of the same miserable heat when I was stuck in the 123

then it came to me that the problem might be temperature related
makes sense
the tumblers are worn out
perhaps a change of temp made just enough difference
between go and no go
so the next morning I when it was cool I went to the car,
got in, turned the key and drove home

as to the WD40 controversy
WD40 should never be used around lock on on boats
it removes lubricants and then evporates
but the goal here is to make the lock work once then replace it
so I don't see it as an issue

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69 220D not running
79 240D parts car
80 240D Beater runs everyday
81 300TD temp disabled cooling problem
82 300SD sweet