2001 Blazer misfires then dies

[sindy1232]

OK, truck would not start and the fuel pump was bad so got it changed. Then a week or so later had problems with the truck losing power and dying and CEL came on. This would only happen once in a while and the dealer said they had to recreate the problem to know what was wrong.

Then one day the truck lost power and died. When trying re-start it the truck was backfiring (misfire?). Took to shop and they said the fuel filter was not changed so they did that.

No problems for a week. Yesterday driving on the freeway and when I turned on the AC the truck lost power started to die and the CEL was blinking. Finally was able to get pulled over and turned off the truck. Waited a few minutes and it started just fine. Truck drove fine for about 20 miles then it died again with no CEL. Made it a few more blocks and died again. Few more blocks and then we parked it for about 30 minutes and started just fine.

This morning I was able to drive the 160 miles home with no problems. I did not turn on the AC or the heat.

Does anyone have any clue what in the heck could be wrong? I am going to take it and have the plugs and wires changed on Monday and see if they can tell me what is wrong.

Thanks,
Sindy

[MT-2500]

If it is missfiring the cel light will blink and there will be missfire codes set.

Check for codes.
And post back codes.

I would recheck the fuel filter.
Was the fuel filter replaced when the fuel pump was replaced?
Did you replace the pump with a AC-Delco/delphi fuel pump or the other brand?
What was in the filter when they changed it?
Black stuff or rust or water or trash?

Get a fuel pressure gauge on it and run a full fuel pressure check and watch the pressure when it acts up or no start.


The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.