92 jimmy 4.3 vortex fuel pump? wouldn't start first attempt then not at all

jimmy would not start on first attempt on three different occasions but started on the second try....the next time it would'nt start at all....i figured it was the fuel pump and i needed a new sending unit(the tubes rusted through and had repairs but no leaks) so i dropped the tank and took the pump and sender out....i am getting power back there (relay ok)...but didn't hear the pump....tested out of tank the pump runs(ground connection seemed fine)....can it run but not have the pressure needed to start????...i know now i should have checked the pressure first but i always could hear the pump when i turned the key on but not since it wouldn't start....could there be low voltage back at the pump plug in????.... it ran and started perfectly before this problem....this is a newer tank and newer pump ...the pump always seemed to make alot of noise when it was new and i notice the screen was worn through as it must have been touching the bottom of the tank(a small slot shaped hole approx. 1/2 inch long)....not any visible dirt in the tank...I ALSO ORDERED A PULSATOR...COULD YOU TELL ME WHAT IT DOES????

I have heard of aftermarket pumps for Jimmys not lasting as long as OEM brands, but I'd also look at the fuel pressure regulator. Not sure where it would be on a '92 though. It was located under the intake plenum for my '96, but your '92 has TBI injection.

You need 60 psi at the rail, the Vortec had major problems with the spider assy and reg. under the upper plenum.

The VIN W engine has the CPI "spider" under the plenum. The fuel pressure regulator (FPR) is under the plastic plenum and on the firewall side of the fuel delivery assembly (the spider).

http://www.autozone.com/az/cds/en_us/0900823d/80/12/ae/32/0900823d8012ae32/repairInfoPages.htm

The older VIN Z engine has the two-injector TBI. The FPR is located behind the injector assembly.

http://www.autozone.com/az/cds/en_us/0900823d/80/12/ae/32/0900823d8012ae32/repairInfoPages.htm

Do you have spark? What is the pressure at the rail? Why are you convinced that is a fuel pump problem?

I agree with Rick, make sure you have good, constant spark. If that checks out, you need to test and make sure you are getting good fuel pressure. The '92 came with either the TBI and CPI system. Each system has different pressures, so you'll have to verify either one. The pulsator in the tank basiclly smooths out the pulsing from the fuel system. You can actually just remove it (thats what the little piece of tubbing is when you get an aftermarket fuel pump), but in my opinion, if I had to replace it, I would.