Hello all, need some help about air getting into diesel. I have a C250TD 1996. There is air getting in to the injector pump somewhere and I cannot find where. It's fine when it's running, but if sitting for a few days, it will fire once or twice then will not run until bled. I have replaced all o-rings on tubes that supply fuel to/from filter/injector pump. I've checked the feed from the tank and I've replaced the injector return tubes but it still gets air slowly from somewhere. Does anyone know of any likely/common problem? Appreciate some help, it's driving me nuts! Thanks Scott