The sending unit is actually a variable resistor.
The suggestion to spray carb cleaner or starting fluid in the intake is a good way to tell if it's an ignition issue or a fuel issue.
The PIP sensor and TFI module are common ignition killers in the old fuel injected 5.0. When the TFI module starts to fail it's known to give starting problems especially when it gets hot but it can fail at any temperature. I believe a failing PIP sensor will also give problems when it gets hot but it will tend to stall out a running engine rather than keep it from starting but it can also just die completely at any time.
It should be noted that cheap aftermarket brands usually fail in short order so if either one of these are the issue don't buy generic crap to replace them.
If it's an ignition problem then another possibility is a bad ignition switch. Many Ford cars from this era had a recall for the crappy design of the ignition switch. My 1993 had it replaced at some point before I bought it but the replacement also loosened up and failed. I believe that Ford seemingly never redesigned the switch and just replaced them under recall with the same junk design. Either that or the redesign just wasn't any better than the original design.
