91 Ranger computer problems

91 ranger 4cyl dual plug coil packs, new battery, crank sensor, computer, plugs and wires. Started first time for about 1 hour , then no fire again. Another new computer ran for about 5 minutes then quit, let set for a couple of hours then will start run for afew second over and over, will get another new computer but seems something else is problem , any help ? thanks for looking.