88 bronco 2 runs when it wants

my bronco 2 runs grate at times it will idel for hours some times, can be going down the interstate and be running top shape then all the sudden it will shut off when it shuts off it has no fule pressure i leave it sit for some times 2 min some times days and it will start i have changed both fule pumps filter ecm pressure regulater fule lines you can hear the pump clicking but wont run any ideas