2001 Expo Wont start in hot weather!

I have a 2001 expedition (4.6L) that wont start when the weather gets over 82 degrees. By not starting I mean WONT START (it cranks over). You can hear the fuel pump engage, I replaced the fuel pump relay, I even tried starting fluid (tries to fire up, but sputters out). Sometimes after pumping the accelerator (I know it's fuel injected) and letting it sit for a hour or so it will fire up. Problem is I have limited funds to throw at this car & it's the daily driver for my family, so if anyone has any suggestions - please help. I also have a 1992 Explorer that recently decided to not drive forward (all the sudden, no warning) - but that's another post!:shakehead

I had a Oldsmobile that was doing the same thing. Ended up being the ignition switch. Hope this helps!
Franco