Thanks everyone, I will get a look at it this weekend. Oddly enough today it didn't do it, nor did it last night, so it's somewhat intermittent in nature. I certainly don't want a runaway diesel situation, so if I end up having to replace the valve I will take precautions. I had to replace that little white plastic valve in my 300SD YEARS ago, so it must have slipped my mind, but I admit I'm not quite as familiar with the inner-workings of my OM606 as I was with the rugged 617.

Thanks for the link as well, sixto. Adding a manual lever shutoff like what my 300SD had certainly would make me feel better in the future, I don't really care of that leaky screw on top of the primary fuel filter.