22re quits after 7or8miles

my 86 22re(4x4pick-up) dies after driving about 7miles or so.I replaced the fuel pump.Checked all vac. lines,Had a leak in the air intake tube,replaced that some line leaks,fixed those.But a relay seems to be getting hotter than normal,I think fuel relay.I was changing it out with another each time and that seemed to work-not anymore.I think it's electrical i.e not vac.or fuel.Even though electrical controls all that.I don't know.Why is it waiting to quit and almost allways about the same time.Then after a while or the next day it will start and run fine...for 7or8 miles,then dies again.Whats happining to my poor baby?

Try driving without the gas cap to see if the vent line to the tank is restricted.