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.
February, 7, 2011 AT 4:27 PM
Some of my info says 54--64 psi. It also says, with engine running, quickly hit the throttle while watching the gage. Should be close to 64psi, if not, replace the spider system.
February, 7, 2011 AT 8:19 PM
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.
February, 7, 2011 AT 9:10 PM
Engine cranking, do you have spark at the plugs? Do you have an injector pulse, use a noid lite.
You should have pressure also with engine cranking? With fuel pressure loose, possibilities, pressure regulator leaking-- fuel injector leak-- pressure is leaking back through the fuel pump. Any applicable trouble codes? Are you fully obd1 compliant?
February, 7, 2011 AT 10:17 PM
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.
February, 7, 2011 AT 10:27 PM
The spider fuel system is noted for problems. Any applicable trouble codes?
I don't think the pressure should leak down like that. I already gave some of the leak down possibilities.
February, 7, 2011 AT 11:38 PM
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.
February, 8, 2011 AT 5:46 PM
Take the throttle body off and clean it, check the iac/ idle air control.
After you build fuel pressure, block the return fuel line, this is just key on engine off, see if pressure holds. If it holds, I'd have to check the pressure regulator. Don't damage the fuel line.
February, 8, 2011 AT 8:49 PM
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!
February, 8, 2011 AT 9:03 PM
As far as the pressure leaking off, no, the cts wouldn't cause that. I don't know anything about your manual. Below is info from MOD about fuel pressure test. That's all I have.