We all(yes even me!) need to be more careful when stating
FUEL PUMP in order of clarity either say
Lift Pump or
Injection pump other wise it;s
Apples and Oranges ,
Now an
Injection pump can get black oil in it from a leaking main
shaft seal into the front
gear case- BUT saying that it's normally the other way around- fuel leaking into the engine oil,
The
lift pump can also be contaminated from a seal/diaphragm issue as it also has
parts of the pump exposed to the engine internal oil- Again how ever it normally
leaks fuel into the oil rather than the other way around,
Cheers Steve