What would cause a dodge ram diesel engine to start hard when parked facing uphill but start easy when facing downhill?

Closely examine the entire length of the fuel line to see if there are ANY pinhole fuel leaks. Even the slightest amount of fuel seepage will result in a vacuum leak and that would cause the fuel line to suck air when the vehicle is facing uphill. If it's a small leak the action of the fuel pump could eventually overcome the leak, driving any trapped air out.