I know this type of thread does not really fit here but I don't see the point of joining another forum just to answer one question.
I am having issues with my 93 s10 blazer. It has the 4.3 vortec with spider injectors. Recently I had to change the fuel pump and it sat up for a few weeks. The other day I tried to crank it up and the pump no longer comes on. When the pump was first installed it came on and worked correctly. After checking the wires going to the pump at the rear of the truck I found that the pump is not getting power. I went back to the engine bay and cheked the pump relay. It is getting power from the fuse box but no power is exiting the relay to the computer or the pump. I changed the relay today and it did not change anything. Does the computer somehow tell the relay to open to allow power to return to the pump or something? I'm not sure where to go from here and need a direction before I replace parts and end up not knowing what works and what doesn't. I might note that the oil pressure unit was broken off behind the intake by me one day while adjusting the timing. Also when it was running before it idled like utter crap and surged off idle while driving. I have a feeling the cat is stopped up and that's why very little exhaust comes out the tailpipe and its very hot exhaust fumes. After the oil unit was broken the truck would still crank so I did not think that could be a problem. Thanks for the help guys.
Jamie

the ecm provides the power to close the relay. if you turn the key off and back on it should stay on 2 seconds before shutting off if the car isnt running

It doesn't come on at all and is not getting power so what can cause that?

First check to see if your fuel pump is dead. You can get wiring diagrams right from the autozone website (and many others). But the sure fired way to test it is by testing the wires right at the plug on the tank.(sounds like you have done that already)
You can also unplug the relay and jumper a wire on the plug to test the pump. And always remember when working with GM fuel injection, that in most cases the computer turns things on and off by completing the ground path (this has to do with high power N-channel FETs being more cost effective). So many things like the injectors and relays are "hot" most of the time. This can trip people up sometimes when using a test light to check for voltage at various places.

So you say you broke the oil pressure sending unit, Thats actually the first place I'd look. Many of the gm efi setups have the fuel pump circuit wired in with the oil pressure sending unit as a safety measure. A 3 pin oil pressure sender is a pressure sending unit and also a pressure switch. Its been implemented in different ways over the years, so check the wiring diagram.
Also on some models there is a fuel pump test port on the ALDL plug, but I dont remember if its directly to the pump or if it just activates the relay(once again check the diagram).

I'm betting it's the oil pressure switch too.

Put 12 volt B+ to the loose red wire hanging near the fuel pump relay and see if the pump comes on.

The red wir goes to the fuse box though and it has power. The greyish wire goes to the pump

Hmm, well I know there was a wire hanging out that was not hooked to anything and I thought I remembered it as being red.

Maybe the test wire that you put 12 volts to to send power directly to the pump is a different color on your car. :confused:

Do you see a wire hanging out near the fuel pump relay?

one things for sure is that you need to fix the oil pressure switch. i dont remember which switch is used for the guage and which one is used for the pump relay without looking at a wiring diagram buta damaged switch could be effecting the relay operation. repair the switch first then if you still have a problem you can start checking the relay out put for power with the key on for 2 sec and go from there. if it still doesnt work i would apply 12 volts directly to the pump to verify its ok before continuing with the wiring troubleshooting.did you use the factory procedure to adjust the timing? why did you change the pump to begin with?

The pump went out several months ago and I had put a aftermarket pump in that did not produce the psi needed to even crank it. I recently put a GM OEM pump and filter in and all seemed fine excpet for it running so badly at idle and surging while applying a small amount of throttle. When the aftermarket pump was still in I first thought the distributor was the reason it would not crank so I changed it out. Did not work so I put the original back in but did not have the timing set correctly I don't think. The other day I pulled the dist back out and was going to reset it correctly when I found the pump was not working. I set it by unplugging the wire under the carpet on the passenger side, then setting it on zero at idle correct?

i dont remeber for that year but the procedure should be on an emission decal on the core support. sounds right. you usually need to disconnect a wire to put the esc in the bypass mode in order to set the timing.did it start running rough after you removed the dist the 1st time?

Yes it did but it could also be a result of other things to. Its a case of changed to many parts and don't know what the problem could be. Could the cat be causing it?

if it started running rough after the dist was removed i would make sure it was installed and phased correctly. are the wires in the correct order? any codes?