91 rs tbi 5.0, when car starts it runs great no hesitation, both injectors have solid spray stream. If car runs for a while and i shut it off i cant restart, engine turns over will not fire, If i try several times or wait 15-20 mins it starts fine. Last time it happened i checked spark it was good, but noticed while i had someone else turn key while its cranking fuel barely drips from injectors. waited 20 minutes tried again and fired right up and injectors sprayed right b4 firing up. changed fuel filter no change. think it could be fuel pump but dont understand why it starts sometimes and not others and runs great when it starts.