The typical Yanmar diesel fuel system is subject to losing it's prime when changing filters. Even letting water out of the sediment bowl can let air in. It can also happen when the boat is motorsailing if the fuel sloshes around and lets an air bubble into the line. This usually happens at the most inconvenient time. It seems like a small reservoir (about 1 quart) installed between the fuel feed pump and the injector pump would solve the problem. The reservoir would need to be higher than the injector pump. Any air in the line would stay at the topof the reservoir while fuel would be drawn off the bottom by the injector pump. That way no air could get into the injector pump etc. I have always found the fuel feed pump to be self priming; so air bubbles there shouldn't be a problem. Also, I think the top of the reservoir should have a hose fitting for connection to the fuel return line. That way the reservoir would have a constant circulation, and automatically purge any air. The fuel feed pump has a capacity higher than drawn on by the injector pump so the reservoir would quickly refill after any air pockets had passed through. It seems like this modification would eliminate most bleeding incidents. I would be much more inclined to drain the sediment bowl if I knew I wouldn't have to bleed the lines. If anyone has any comments on this please let me know.