I am making a distinction between repair and rebuild since I did not open up the pump end of the pump where the feed pump is or "mess with" the high pressure pump. The fiber retaining ring for the governor weight retainer had broken. As it disintegrated fibers from it blocked the check valve in the fuel return line. This cut off the fuel so the engine would start and IMMEDIATELY die.
I removed the pump, a JOB just by itself! Took it apart (not by the "book") so I could get at the governor weight retainer and replace it. I did replace various "O"-rings as I put it back together, though most of the rings looked in excellent shape. I don't think the pump had that many hours on it. The shaft bushing in side the front of the pump had no detectable groove where the umbrella seals rub so I left it in and reused the seals. Where are two images of the remains of the retaining ring. And the plugged check valve.
What I did was sort of like replacing the friction disk in the clutch, a repair. Where even though you might have the engine and transmission apart, you would not rebuild the engine if it did not need it.
