Is there no oil pressure as verified by looking into the valve cover (meaning no oil flow)?

Or is there no oil pressure as indicated on your oil pressure gauge?

If it is the latter, it may be your oil pressure sender. This little device is located under the oil filter. Access is a pain on a OM603, W124, and probably similar on your SD. It has only one wire that runs to it. Search on this website and you will get directions for where to find the sender. And if it is the problem, when you disconnect its wire, the indicated oil pressure will peg at its highest level. Then you have found your problem, and the new part costs $50 or less (depending on what brand you need). Hope this is your problem, because it is alot easier/smaller job than if you actually have no oil pressure.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).