89 balzer not running

i have a 89 s-10 blazer. it was running fine and then one day it wouldn't start. when it starts it runs great. i have replaced the fuel pump, fuel filter, and checked the wiring to the relay. you can hear the pump running sometimes and the pressure is up when the key is on but drops right back down. i can't start the blazer so i can't check the idling pressure. can someone please help???

I had a similar problem with my 89 Blazer. Turrned out to be a combination of fuel pump and clogged injectors. Do you get a good atomization in the injectors when turning it over? I ended up buying a TBI tune up kit and completely cleaned the throttle body and injectors. That did the trick, and I noticed a significant increase in power.

could also be the regulator