1993 s10 blazer wont start

i have a 1993 s10 blazer 4x4 4.3l vortech automatic.problem is it wont start.it is firing at the plugs.i have replaced ,(everything new) fuel pump,filter,central injection unit,ecm,distributor cap and checked and replaced any blown fuses. some one had broken the steering column and ignition switch i replaced all that with no change.it will start and run when you pour gas in intake but will only run until that burns off.i have checked and replaced everything that could possibly keep it from running obviously i am missing something somewhere.any help would be greatly appreciated.:banghead:

Try checking the feul pressure at the intake. Not simply having enough or none at all. That sound like your prob. No Fuel. Try turning your key to the run postition and see if you can hear your feul pump.