What's Up or Down With This Car?

I have a 1998 windstar that will not start when I park it with the front end of the car pointed downhill. When the car is parked on a flat surface it will start. I’ve had the fuel pump and filter replaced about 2 months. can you think of anything else I may need to do?

Gunk in the fuel tank? Problems with fuel pressure? Do you get spark?

This sort of thing can be tricky. I remember the Brothers some years ago had a weekly trick question involving a car when parked on the hill the battery ran down over night. When parked on the level, it did not. The solution was a mercury switch under the hood so when the hood was raised the underhood light came on by itself. When it was parked on the hill, it came on and ran the battery down.