My engine will not idle?

It's a '95 Blazer 4x4 4.3L Vortec, it will fire but stalls immediately. Checked for fuel in upper intake and nothing is there. If I keep my foot on the gas it will stay running at about 2,000 rpm, as soon as you let off the gas it will idle like a dragster for a second and then die. Today I went out and started it and it idled for about 30 min, shut it off and waited a few hours and now it's acting up again. Put a fuel pressure gauge on it today, turned the key on, the pressure goes up to 62 but drops down to around 25. The books says it should hold steady between 58 and 64 with the key on.

I have the same issue with mine. After about 6 months of putting up with it. The truck would not start unless I hammered on the bottom of the gas tank whule trying to start it. Acouple weeks later I replaced the Airtech fuel pump with an AC Delco fuel pump that comes with a different sending unit than what the Airtech has.I was told blazers came with airtech brands. But this is my 3rd fuel pump in 4 years. So I went with AC Delco. It did not matter.I still got the same problem BUT not as often. I replaced the Idel sensor. That did not matter. I adjusted the idling screw higher. That helped for a while. The final result has come down to that it will mostly keep running after start up regardless of the way it is started but if I stop at a red light the RPM will drop low ( below 1/2 )and idle low and check gages light will come on then truck will SOMETIMES die at the traffic light unless I barely hold the padal down enough to keep thr RPM above 1 and the gages light will go back off then push the gas pedal normally to get moving without restarting. I just live with it and adjust the idle screw for higher RPM 1 1/2 on the gage. Try adjusting the idle screw a little higher and see where it does from there.

The problem is I can't get it to start and idle. My book says turn the key on and pump should run for 2 seconds then shut off, which it does. Then the book says after the pump shuts off the pressure should hold steady, which mine doesn't do. It jumps up to 63 when pump comes on but, as soon as the pump shuts off it drops to around 25 then slowly keeps dropping. It gets to 20 in about a minute, am I doing something wrong? I'm doing what the book is telling me to do.

I have spark, and the pressure while cranking pulses about 55 to 65. If I go out and activate the pump by turning the key on, and do it 4-5 times and then try and start it, it will start and idle really rough for about 5 seconds then die.

No trouble codes, don't have a scanner. I can get it running if I pump the gas pedal when trying to start. After I get it running if I let off the gas it will die, but, if I keep my foot on the gas I get it to stay idling at about 1,000 rpm with little pressure on the gas pedal. But, it idles like it's missing a plug. If I rev it up the motor smooths out to perfect. While idling the pressure is around 62, but, if I rev the engine the pressure drops to around 52-55. Another problem is while I have my foot on the gas to keep it idling it will rev up to about 2,500-3,000 rpm and then back down to 1,000 rpm all by itself.

And thank you for answering back.

So, I have to block the return line? Why did the book not say this? It just says to turn key on, pump should run for 2 seconds, which it does. Then the pressure should hold steady, which mine doesn't do. How would I go about blocking the return line? Do I need a special tool?

Quick question, could the CTS (Coolant Temperature Sender) cause this to happen? Someone suggested I check it.

The engine is a 4.3L Vortec CMFI

Thanks again for the help!

Starts shuts off after a minute.

I have replaced fuel reg fuel pump ok with in specs new distiputor plugs wires coil it wont start unles I use starting fluid I know, bad, but when it starts I cant get it to idle I have checked all the vacum lines there good could the egr keep it from starting are not let it idle i'm at a loss please help or could the distiputor be 60 out and fire or is it like most chevy distiputors and either 180 out or on

The injectors are a spider assembly plastic no power accept to the cpi it self

My truck all of a sudden is having a issue wanting to stall when I come to stop and hit the accelerator. If I don't pulsate the gas pedal by stepping on it and letting it off and stepping on it again. It acts like it getting way too much fuel. Because I noticed I used three quarters of fuel to 162 miles. I've changed out alot of stuff. I'm lost and need help please help me

I have fixed the o2 senser, oil pressure senser, oil pressure sending unit senser, spark plugs, had the chevy dealership look at it and he said that the exhaust manifold gaskets could cause that. Also had them run scanners and they said it was the the o2 senser that it was reading and all of my electrical was good in the truck. And even they checked the fuel pressure at the fuel line by taking off the fuel filter. But the problem is i've already spent 400 dollars on the truck in two days and still haven't got no where. I was just curious if it could be the fuel pump relay, the fuel injector regulator, fuel filter or the fuel injectors its self. But how do I test each one of them with out the equip of a guage. Their expensive.