Newt

Hey I was wondering if anyone could help me. I am currently rebuilding my 87 chev single cab short box and installed a 350 edelbrock crate motor in it. The issue i am having is I can not get any fuel pressure at the carb (pressure guage). I've dropped one of the tanks and changed the pump as well as changed the tank selector switch. When i cycle the ignition I can hear the pump turn on for about 3 seconds and than turn off. I can keep turning it over all day without it building up pressure so it won't start, its like the pumps dont keep running. Prior to this after about 5 minutes of trying to get it going it would finally build up pressure and start so thats why i changed the pump because i thought maybe the check valve was passing and as soon as i shut it off the fuel would leak back to the tank. But now it will not fire at all. Also their is a regulator to drop the pressure for the carb. Any suggestions on what i should try next?