I just changed out my fuel filter on my '96 300D because I suspected it as being the culprit of my non-starting engine when I made a strange observation... I expected it to be full of diesel but it was almost empty when I removed it (and I did not spill any). The tank is about 2/3 full and the car was running fine when I parked it.

Now here is the kicker... I parked it at an incline overnight (say maybe 15 degrees) and that's where the problems started. I've only had the car for 7 days now and it's always been parked on the level. 2 days ago I parked it on the inclined driveway and the next day had a hard time starting it. After another night on the incline it wouldn't start at all the next morning.

Is is possible for the fuel to flow back into the tank if the engine is at a greater elevation than the tank for an extended period of time???