I have a 96 blazer,4.3L 4wd that has been running great up until friday. Would like any input on possible problem.
I was low on fuel and pulled into and filled up at a station that is 2 blocks away from my home. I drove home no problem. 2 hours later I decided to run down to station again to get some treats and after 1 block truck died and wouldn't even try to fire.
pulled it back home and have ignition and all fuses good but no fuel pump. checked pump relay and no power to relay coil pins. Have not been able to figure out where this signal comes out of the pcm to see if it's the wire or the pcm or can it be something else telling the pcm to shut off this circuit. Checked obd codes - none . The pump will run when jumped and I can jump the relay and the engine will run real good for about a minute then acts like it runs out of fuel and dies. I have changed the fuel filter and am going to check fuel pressure tommorrow but was wondering if I am wasting my time and just need to change out the pcm.
Any input and suggestions will be greatly appreciated

Do a fuel pressure check also and find out the fuel pressure specs are.If it is a fuel pump,stick with a Delphi pump from the dealer or a Carquest parts store.Carquest's fuel pumps are now made by Delphi and last longer.

Will check it out, thanks

Do a fuel pressure check also and find out the fuel pressure specs are.If it is a fuel pump,stick with a Delphi pump from the dealer or a Carquest parts store.Carquest's fuel pumps are now made by Delphi and last longer.
I agree with Wafrederick. You should always use OEM Parts. If your not getting any thing at the fuel relay. You should take a look at your ignition switch module. The 96's have been noted for that type of trouble. One of my 96 did the same thing. Ran great then just died. No power at the relay. Changed the ignition module and she was in top shape. Post back your findings. Heres a link on how to replace the module.
http://www.automotiveforums.com/vbulletin/showthread.php?t=287636&highlight=ignition+module

I know about Airtex and Carter fuel pumps,junk.Put 6 in one Chevy truck when Airtex was Carquest's fuel pump supplier.Airtex will not warranty a defective fuel pump 99.9% saying it is installer error.Replace the fuel filter when replacing the fuel pump also,you do not want dirt and garbage going in the new fuel pump and burning it up.That is part of the warranty of a new fuel pump most of the time.

I have a 96 chevy blazer 3 weeks ago it started getting hot out side and it quit starting u could let it cool and it would start again. I could hear fuel pump running would not, start pour gas down throat starts and dies. I parked it in the yard let it run with air on for 45 minutes got it to fail to start hooked guage to it fuel presure at 42-45 pounds sits for 15 minutes presure goes back up to 56# starts right up. Low fuel presure delphi pump 14 months old replaced it runs 2 weeks ambient temp gets up around 90 truck starts to lose power will run without air dies with air on drive a week no air on truck dies when hot. have cleaned all terminals voltage guage staying close to 14. have same problem as before truck hot presure goes down in 40's won't start let cool or drive in the morning no problem fuel presure around 60 afternoon gets hot outside presure drops off around 45 won't run have let it run at autoparts store till it dies hooked up cumputer shows no trouble. can't figure this one out. HELP

I have a 96 chevy blazer 3 weeks ago it started getting hot out side and it quit starting u could let it cool and it would start again. I could hear fuel pump running would not, start pour gas down throat starts and dies. I parked it in the yard let it run with air on for 45 minutes got it to fail to start hooked guage to it fuel presure at 42-45 pounds sits for 15 minutes presure goes back up to 56# starts right up. Low fuel presure delphi pump 14 months old replaced it runs 2 weeks ambient temp gets up around 90 truck starts to lose power will run without air dies with air on drive a week no air on truck dies when hot. have cleaned all terminals voltage guage staying close to 14. have same problem as before truck hot presure goes down in 40's won't start let cool or drive in the morning no problem fuel presure around 60 afternoon gets hot outside presure drops off around 45 won't run have let it run at autoparts store till it dies hooked up cumputer shows no trouble. can't figure this one out. HELP
First of all. Welcome to AF. You need to start your own thread. Just from what you have said. It sounds like your fuel pump is over heating and needs to be replaced. Is your gas tank above 1/4 of a tank full? You should never run it below that. These fuel pump use the gas to keep cool.

Ok, I did the fuel pressure test and have 62psi w/pump running and drops to 54psi w/pump off. System will hold this pressure steady. book specs this to be aprox 55-61psi running so feel fuel pump is good. :confused:
Still no voltage at pump relay coil.

Ok, I did the fuel pressure test and have 62psi w/pump running and drops to 54psi w/pump off. System will hold this pressure steady. book specs this to be aprox 55-61psi running so feel fuel pump is good. :confused:
Still no voltage at pump relay coil.
How long did it take to drop down to 54psi with the ignition off? 54psi is actually a little low and can cause your motor to stop. Are you still not getting 12V at the fuel pump relay?. If so, I would still say that it your ignition switch module that giving your trouble.

the pressure is as soon as I shut pull the jumper off the pump. book says a 3-10psi dropis typical. no voltage at relay

are you referring to the module that is located up on top of motor close to alternator?

I could not figure out how to start a new thread. Tank is 3/4 full car starts losing power when driving then dies fuel pump presure is 40 -45 psi will crank but not start wait 1 hr presure goes up to 54-56 starts runs wait till morning presure 60+ holds good till afternoon when it heats up outside then it starts to drop until it gets in the 40s and will not continue to run. I will go back and find out how to start a new thread it says somthing about my html not on

There is no ignition module in the 1996 and up 4.3 distribitors.Check for spark and if there is,not in the ignition system.It has the cam sensor inside and the signal to fire the injectors.Try doing this,spray starting fluid in the throttle body and and have someone start it up.If it starts and quits,bad fuel pump.GMs will not run under the lowest fuel pressure.

Well, installed new ignition control module. still same thing. I can jump the fuel pump and truck will start and purr for 30-40 seconds until computer shuts down injectors. will barely idle, hit key again and will purr for 40 seconds. :banghead:

are you referring to the module that is located up on top of motor close to alternator?
Its located inside the steering colum. Right behind the ignition key. Here is a link that will walk you through the replacement of it. http://www.automotiveforums.com/vbulletin/showthread.php?t=287636&highlight=ignition+module Hope this helps.

Is the signal to the fuel pump relay coming directly from the module? because all circuits lists thru the fuse box are working correctly. My repair manual shows a ignition contact for this circuit but states it's location is in PCM.

Is the signal to the fuel pump relay coming directly from the module? because all circuits lists thru the fuse box are working correctly. My repair manual shows a ignition contact for this circuit but states it's location is in PCM.
I don't have the drawing in front of me, but when my 96 had this troulble. I went through the same isolation process, and found that the voltage to the fuel relay was provided by the Ignition switch module. This switch module is a major flaw in the 96 & 97 blazers. It causes all types of problems.

Does this vehicle have anti-lock what you are describing is what the antilock does shuts power to the injectors. Try another key or clean the chips on the key with brake clean try using a q tip and clean the switch.
Look for a forum on using a resister to bypass also check GMC. If the pump is wired direct and power to the injectors is cut I'm almost sure this is your problem.

Yes it has antilock brakes, and that's what is baffeling me on why jumping the pump that the computor is still shutting down the injectors after a short period of time. I will replace the switch tommorrow.

I meant anti theft system not the brakes. You can do a google search and bulldog security has some sketchs. You have to do a reprogram if the resistance is different in the new ignition switch. I also think you will need a deep e4 torx socket. Kd and Lisle sell them. Search e4 to e10 for the K-D set.
Lisle just sells an e4.
This is why I suggested cleaning the key with brake clean and using a q-tip to clean the switch. Also try a different key. This system has a chip on the side of the key newer vehicles have it in the switch.

no anti-theft on vehicle.

New ignition switch install. No change to problem.:banghead:

Check for spark if the computer looses reference it will shut off fuel.

Well guys, I went to eautorepair.net and got real electrical prints to my blazer and problem tracks back to pcm. Having one flashed and hope to have it in the vehicle soon. Thanks for you input.