If it continues to be diluted with diesel, you will want to have it serviced. It could be as simple as o-rings or a cracked diaphragm. Even so, there is probably a vent on the side (maybe the backside) of the pump. As diesel invades, it will push out the oil, dumping diesel and oil in the bilge. I don't agree with the "if it ain't broke, don't fix it" theory. If it is leaking diesel into the oil, it will wear out sooner, much sooner. I had a 4 cylinder Bosch pump rebuilt this summer for a little over $700. That sounds high, but for my application there are no new ones available and to purchase a rebuilt one would have been double or more. Why wear out the cam, pistons, etc by continuing to allow the oil to be diluted? In my book, a diesel injection pump is too valuable to "just let it work as long as it will". Yes, I'd try it with a reasonable oil change period. I'd check it regulary. If it is filling with diesel, I wouldn't hesitate to pull it or have it pulled and serviced by a qualified shop.