"il faut" is the il/elle at the present time for the verb "Faillir" and "Falloir" But their meaning are totally different. Fallir : to fail something Falloir : it is when you have to do something, express a need As a french people, I never read or say the verb "Faillir" at the present time. And i didn't know it was also "il faut". So everytime, you can read or hear "il faut": it will always be the "Falloir" verb that express something that you have/need to do.

Maybe you said "failler" because you saw the subjunctive form of the verb "falloir"? It would make more sense! :) http://en.bab.la/dictionary/french-english/il-faille