Fuel Pump Issues?

So I have a couple questions, it's me again, that 94 Blazer that I ended up putting a new engine in. It still had problems starting, though not really running, and I took the advice of checking the CPI injector, and the regulator. From what I could tell, the regulator was leaking a little bit, and so I decided to go ahead and replace the regulator. Then I decided since I was already there, to go ahead and replace the whole spider assembly. The vehicle started right away all that day, and I was pretty convinced the problem was fixed. Now it's started again, and it's worse than ever. It took me almost 5 minutes to get it started this morning.

I suspected the fuel pump all along, but here's where my question comes in. The link that I received, and that I read up and studied, said that the fuel pressure KOEO, the book says should be 58-64, and the guy said you need 63-64 to have it running like it should. He also said that the fuel pressure should bleed off slowly, if it bled fast, there were issues. I get 59, 59.5 PSI even, and it bleeds maybe 1 PSI per 2 minutes. So I don't think it's bleeding off too quickly. When I turn the key on, sometimes the fuel pump turns on, and sometimes it doesn't. Lately, it doesn't more often than it does. And if it doesn't turn on, the engine refuses to even cough and try to start. When the fuel pump DOES energize, it starts right up. And the pump runs all the time KOER - which is normal.

So my question, does it sound to you all like the fuel pump is failing? Or more like a wiring / signal malfunction, that something isn't telling the fuel pump to energize.

Also, the schematics in the Haynes repair manual that I have, show's a "Fuel Pump Pressure Switch" but I see nothing elsewhere in the book, or in the car. So on a '94 4.3 Vortec CMFI VIN-W is there even a Fuel Pump Pressure Switch? I'm looking under CMFI and it shows in the schematics, but the schematics are kinda shady, and I can't locate it otherwise. So is there one, and if so, could ya tell me where it is? Cuz the pump relay is fine.

Thanks so much in advance, everything is working very well on the vehicle, with this smal exception.

i would replace the fuel pump, sounds like that is the problem, and is not that hard to do.

Fuel pump...

When you can't hear your fuel pump. Do you notice if your dash lights are on (ABS, Serivce Eng., Seat Belts, ect.) If you don't see them. I would say that your ignition switch is bad, and you need to replace it.

Replaced the fuel pump and strainer just now. KOEO it's putting 56-58PSI out, which is really low, it's supposed to have 58-64, and recommended to have 64. It only has pressure issues when it's cold, and it's warm now and starting fine, so we'll see. Only problem is, we're dropping this Blazer off tonight, back at her house. I have a bad feeling she's going to call tomorrow and say that it wouldn't start.

But what else is left? We've replaced the pump, the entire injector assembly, regulator included, spark plugs twice, fuel filter, drained the tank and put good gas and some dry gas and such in it. Unless there is a fuel line leak, I'm pretty lost. But I don't believe there is a fuel line leak.

Also, I'm still totally baffled about that "Fuel Pump Pressure Switch" I have no idea where that is, and if that might be affecting my poor fuel pressure.

Thanks again.

56-60 at start, so you're within that range... 61-65 at running... If it's still low you might wanna make sure the cpi isn't leaking in he upper plenum..

Too late for this, but there is a connector at the top of the gas tank, inside, that gets corroded and loses connection. Really baffled me. Hope you have no more problems, but if so you'll need to pull tank and check this. Have you replaced the actual fuel pump relay? There are two of them side by side above the brake booster as I recall, you can just switch them and see if it fixes the problem.

The fuel delivery changes quite a bit with just a slight change in pressure, the unit flows 28% less volume at 55 psi compared to 60 psi. When testing the fuel pump you should see 58 – 64 psi with the key on, engine off (KOEO), this pressure should hold fairly steady after the pump shuts off. If it bleeds down quickly, then there’s a problem. The pressure should be 52 – 54 psi with the key one, engine running (KOER)

So I wasn't within range, although perhaps the gauge is just off, it's a few years old. As for the CPI, those I replaced, I found the regulator leaking. I replaced the fuel filter, the fuel itself, the CPI injectors, lines, and nozzles, the injector regulator, the fuel pump and the strainer. Not to mention the engine itself, so the pump was the last thing that it possibly could have been, as far as I can imagine. Although, seeing that fuel pump pressure switch in the schematics really led me to believe there could've been something else. Nowhere to be found, no one has heard of it on a 94 Vortec 4.3 Vin W. Thanks though.

As for tom3, there was no need to replace the actual relays, firstly the pump ran fine with the engine running, and mostly fine with the key just on run, secondly I checked the relays, all of them, not just the one for the fuel pump. Thanks for the tip though as for the connector.

Yeah, I pulled the tank, put the new pump in, and it started like a champ early early in the morning, cold as hell, so we're all completely squared away, that was a nightmare of a chevy crash-course.

But thank you all for your tips, you've been most kind.