Even with a half tank of gas , car won't start if even on the slightest downhill angle. Had this problem years ago when I was parked downhill( pretty good slope) with only a couple gallons of gas but not since then. Is this a normal problem for these models of Olds?

Quite possible, the fuel pump sock may be kinked in an upward direction....if this happens, with the car at an angle, that sock could lift it'* "head" above the level of fuel, and you are sucking air into the pump......

Thanks