how many miles on the car?
Do you know any of the service history?
Hopefully your just having fuel issues, but it seems more likely given the rpm's you were running that the pump jumped time.
If as you say, you had to adjust the pump to its max allowable adjustment to keep it happy..
There's a very good chance the timing chain stretched, or the upper guide rail broke and allowed the chain to jump time on the pump drive.
I've had it happen on a 190D.

When your engine cranks, does it have an "even" sound to it, like it has compression in all 5 cylinders?
As someone else asked do you see the camshaft turning when you crank it over.

Usually when the chain lets loose at highway speeds, its all over but the crying.
Service interval if I remember is 150K on the Diesel's chain.

If your careful and check the chain and don't see any slop in it. .you can run it further.
Do you know how to do the "drip" test for pump timing?



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