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Re: Fuel in oil - where to start?
I don't know the MB10A at all, but generally there are only two ways a lot of fuel will get in the oil. The ruptured diaphragm, which you say is out of the loop and can be eliminated. And then, loose rings, allowing fuel to enter from the cylinders.
If the fuel is just "traces" picked up during an oil test, that can just be from short engine runs that don't cook off the normal fuel and condensate accumulations. In which case you just run the engine longer to burn them off.
But if there's gross fuel contamination, I'm come back to looking at the rings. A compression test, and a leak-down test, to see what's really going on. Bad rings, low compression, that would also contribute to "hard to start", so more dots connect up at the same time.
There are only so many places where the oil "spaces" and the fuel can cross into each other.