Here what happend my sisters friend has an 86 f150 with the 302 fi aod . She drove it to school ran fine . Latter in the afternoon she went to leave it wont start calls me. I check it's geting gas no spark at the plug. Check the coil it's getting spark and the rotor turns over. here frineds brother a dodge mech come in and says there is a weak spark at the plug and the cap and rotor are bad. So shes goes to the part store cap and rotor still no start anyone have any ideas.

 

Could be the TFI module on the distributer. The are known to go bad, or it's spade terminals corode, or are to loose to make good contact. Take the TFI module off, see if it is corroded, burnt etc.. I think you can bench test them, but swapping it with a known good one for trouble shooting is just as easy.