Odd problem with '02 fuel system
 

Ok so I'm totally stumped. I have an '02 Blazer 2 door 4x4 with the 4.3 votec motor in it. I was driving along last week and it just bogged down on me and stopped. I got it off the side of the road and it wouldn't start. I got it towed to a friends house and it's been sitting there since. It will crank just not start so I checked the fuel pressure and I had none. I checked all the fuses and they all seemed fine. Checked the relay (actually I swapped that relay with another one in the fuse box, same model number and everything) and still nothing. So I assumed it was the fuel pump cause it has quite a few miles on it. I dropped the tank and swaped it out and still nothing. I pulled the tank down again and here is where it gets odd. I had a friend turn the ignition to the on position and I get power at the plug for the fuel pump, but it is only for half a second. It wouldn't even read on my multimeter so I just used a test light and the light only blinked on. I am totally stumped now. Any thoughts? The security light that I've read about on here is NOT on. The check engine light is on, but I haven't had a chance to get a code reader and go to where the truck is to see if I can pull it. Sorry for the long post, but I figured the more information the better. Any ideas you can give me would be much appreciated because I am totally out. Thank you.

Try swapping the fuel pump relay for another one like it in the underhood fuse/relay center.

Maybe the relay you swapped out is bad.

That's what I did. I pulled the one out for the horn and swapped it with the fuel pump one and still nothing. And I did try it first and the horn worked and even after I swapped them out the horn work again so I'm assuming the relay was fine.

The next thing would be testing for the relay trigger and supply power with your DMM (digital multimeter). You could also test the continuity in the + power wire to the pump and the continuity from the ground pin in the plug to a good frame ground.

I'm not sure what you mean about the relay, but I did take a multimeter back by the pump and I had 12 volts the first time, then when I had him turn the key off and do it again my volts only went up to like 5-8 but like I said, it only happened for a split second and then I lost power, so I don't even think the multimeter had a chance to read what the highest was. That's how quick the power came on and went off. Thanks for help, it's good to know I've been looking in the right spots also.