I personally find it hard to believe that the compression in all four holes has dropped equally to around 50psi over the life fo the car...
That being said I am not there and cannot verify this with my own compression test but sheesh, that seems really odd.
it almost sounds like their gauge or hookup to the tester was bad and thereby measured a consistant 50psi as that is all the bad connection could hold.

Maybe someone can comment but I wouldn't think that it would have even come close to starting at 50psi or let's say 75 psi as it was on it's way down... I don't think it could have created enough pressure to fire off the fuel mixture.

Anyone ever done the math on this to figure out the compression/heat ratio and burning point of diesel at ambient temps?

I hate to think of a fine car like this finding it's way to the wrecking yard but I also understand that a motor is not cheap.

Before you donate or junk it check around here as there are a few of us that like a challenge...

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique