Failed oil pump?
 

Put my '88 300SE on the road after rebuilding the fuel system and I'm right back where I started. The engine was running great then a single "thunk" then the engine died. The engine would turn over but would not show any oil pressure.



Engine oil was full. At this point I suspected the timing chain. So I pulled the front cover off of the engine and inspected the chain. Everything looks good. The guides looked to be in good condition. Chains and sprockets looked good with no obvioous wear.


Short of dropping the pan and pulling the oil pump I'm at a loss. Anyone have any input?

How did it sound immediately before the "thunk"? Was the oil pressure good? What is the oil level?
When you say it would turn over, does that mean immediately after the "thunk" the engine would crank using the starter but not ignite and run? Internal M103 engine problems are kind of rare.

Good luck!!!

The engine was running great. Oil pressure was at idle, 1.5 bar with the engine at normal 80 deg C temps. Anything above idle pegged the needle.

The oil level was where I started, full. The engine would turn over but not start and run.

The top end is in time with the crank, and when the crankshaft is at TDC the "hole" in the cam lines up.

Looks like I need to drop the oil pan and pull the oil pump.

Wait...let's discuss...

If there weren't any knocks/taps/odd sounds prior to the "thunk" I wouldn't suspect an oil pressure problem. I'd suspect a fuel or spark problem.

A compression test is in order after a spark test.

Good luck!!!

How about the oil pressure sending unit?

It's best to remove it and insert a mechanical test gage. Most US cars have a 1/8 NPT thread, but I don't know what thread Mercedes uses.

Also check for spark and fuel pressure.

Duke

"Failed oil pump?"

Nope. Everything that has stopped working is electric; injection, ignition, instruments.

I am not surprised that the starter does not crank the engine fast enough to show oil pressure. I don't know your engine but engines usually start with low oil pressure so I would not think that would be the cause of the failure to start. I agree with the advice you have been given.