some fuel pumps have a little breather hole in the top of them,,about the same size as a panneling nail diameter,,,if you have excessive crank case presssure,,and the fuel pump body is an offcast,,,it can come squirting out of that hole under heavy load,,it will come in behind the actuating lever,,and through the body of the fuel pump,,,some gaskets will allow the oil to pass through,,,,,haven't seen this phenominon in years,,but i used to see it happen.