Get the factory manuals.

The wiring changes slightly during the W126 production run, and you will need to look at a diagram that includes at the oldest and 1986 model.

Did you try to turn your key slightly counterclockwise and see if the chairs and column work?

Oil pressure at hot idle can be as low as .5 bar per the factory.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles