Ingintion problem

I have a 1993 thunderbird 5.0 and im experincing a problem in which the car is not starting after sitting for over 7 hours or more.what's happening is that it'll crank but the car wont start.when its acting up this way the rpm needle is non responsive, meaning their's no movement. Ive check to c if theirs fuel and their is.i then removed a cable of a plug and placed it near metal and im seeing no spark what so ever so i then gave the car a tune up by changing the spark plugs,cables, ignition coil,ignition control module,distributor cap and rotor and also the eec relay and the problem still remains.the distributor is spinning so im guessing its not the distributor., the frustrating part of it all is that the car will start right up with no problem if u let it sit long enough and once its on i can drive the car anywhere, turn it off and on as many times as i please, but once i let da car sit for a while(7 or more hours) their's the problem again... Im running out of patience and despretely need ur help..PLEASE