Ok, here's the deal. 2000 Blazer 4WD, 180,000 miles, automatic.
Cruising down the highway at 60 mph, ambient temp is 95 (roughly) degrees. Truck acts like it is running out of gas. Kick it up into neutral and give it gas and it and shuts down.

Fuel tank is half or better. Fuel pump does not run when key is turned on, but runs when key is turned off, engine cranks, but will not start.

Let it sit for 20 minutes or so, fuel pump runs when key is turned on and when key is turned off. Engine will start, but it sputters and usually dies. After about 45 minutes to an hour or longer, fuel pump runs when key is turned on and then off, engine cranks and runs like a top.

No check engine light or codes in the ecm. I am a mechanic, but do not have a whole lot of expertise with this fuel system and i don't want to needlessly change parts because i haven't gotten my stimulus check (yeah, right) yet.

From looking at the parts house pages, i know i have a fuel injector pressure regulator, fuel pump, fuel tank pressure sensor and a fuel pump relay.

It's almost as if the pump is getting hot and shutting down. No fuses are blown.

I have checked the ignition system and there are no issues with that.

Any thoughts or suggestions would be greatly appreciated. I am a volunteer firefighter and this is my daily driver, response vehicle and one of my babies. My other is an 08 XL883C so i have a great other vehicle, but i need my blazer. Thanks!

 

Take a look at the 'sticky' threads at the top of the '2nd Gen Tech' section, read through and follow the steps in the ones for fuel system and no-start problems. You also might want to have a place like AutoZone test the ignition control module (ICM).

 

Sticky threads???

Ohhhh, sticky threads...

 

Sticky's are the permanent topics at the top of the forums above new posts.

nevermind

 

okay, now for an update... dropped the fuel tank today and installed some fuel line from the outlet to the return on the fuel pump. Let the pump run for almost an hour with no defects or issues. Put everything back together and cranked it up. Ran like a kitten for about ten minutes, then the same thing. Fuel pump relay in the fuse box was almost too hot to touch. Swapped it for the rear window relay and after a while, it started up, but after 10 minutes, the same issues arise. No check engine light, no codes. Any thoughts?

 

Harry, im having the same exact issue. Im also at a loss as to what the problem is because it only acts up after a longer trip (50+miles) on a hotter day (80 deg ambient +).
It is also hit or miss as to whether it will happen or not, and it is really impossible to tell exactly when it is going to die. So as luck would have it, it has died in the middle of an intersection each time it dies so not only do i have no tools to diagnose the issue i cant because i am in the middle of an intersection! The only thing that i have done is press the schrader valve on the fuel pressure test port to ensure that there is fuel pressure, which there is. No idea how much pressure or whether it is enough to fire the motor.

Then after sitting for 20min or so it fires right up again and drives fine. then i cant duplicate the problem for troubleshooting. It is really starting to **** me off though! I have checked the fuel pressure after it gets going again and it is about 55-60psi which is normal. So i definitely feel that this is some sort of heat soak issue either fuel or ignition related.

Let me know if you figure it out!

 

Wish I had the answer, but just the same problem. Almost exactly after 20miles on every hot afternoon, truck dies and I coast to the side. My theories are overheating relay, overheating wire to pump, or overheating IGNITION SWITCH.

Pulled the ignition switch to replace it on Saturday, but I broke the white plastic pin that rotates the switch (returned the switch I had, ordered complete kit from rockauto). I should know in a week or two if the ignition switch was my culprit.

I might splice a toggle switch inline on the ignition switch harness for the time being to keep the fuel pump engaged... I'm leaning towards this being the problem because it's a common known-issue according to the forum. When my car dies, the fuel pump won't kick on for about 20 seconds (second or third try, I usually hear it whine).

1997 blazer.

 

the relay being "too hot" is just because everything is too hot to touch under the hood when driving on a HOT summer day. I checked my relay the other day when it died on me and ALL of them on the fuse panel were very hot.

I am 100% sure that this is a heat related issue, thursday it was 90-95*F here and my truck died on me about 5 times during a 10 mile trip. I went and got a fuel pressure gage yesterday so that I can see whats going on when it dies out. Yesterday it only hit about 80*F and was raining, I aimlessly drove the truck around for about 70miles trying to get the damn thing to duplicate the problem from the night before! But i had NO luck, drove fine and fuel pressure was fine when i got back home.

I am certain that it is NOT an ignition system related issue because on thursday night when i got it home it wouldnt start again, so i sprayed a bit of ether starting fluid into the intake, it ran for about 10 seconds until the ether burned off. I know that this isnt "proper" diagnosis but I just wanted a fool proof way to eliminate the ingition system as being part of the issue.

Also, yesterday I checked the fuel pressure with the gage, right at 60psi on start up, about 55-60psi when running depending on RPM. I left the system primed w/key ON for about 5 minutes and noticed no fuel pressure decay. I am going to go through the whole diagnosis procedure in the sticky today. My fear is that I will not be able to duplicate the issue since it is only going up to about 80*F today and i only seem to have issues on 85*F+ hot sunny days.
I am completely stumped, and have no faith in driving this thing anywhere!

 

This sounds like a problem I was chasing with a GM van. This'll sound silly but carry a 20oz bottle of water with you. When the truck dies slowly pour it over the VCM and wait a few minutes, does it start? It gave me confirmation to replace it. The other thing too is pull the fuel pump relay out and really look at those connections in the fuse box (those flip down magnifiers you wear on your forehead really help). Pull a different relay for confirmation on how they should look. If the connectors are pushed in that can cause this problem too, it's the same wonderful design they use in the connector on the top of the tank.

 

I agree it is heat related. I deleted my earlier post because of a glaring error where I theorized that due to a faulty ignition switch or PCM that the fuel pump may be getting 24 volts as a result of the PCM continuing to send start-up voltage after the car starts. This isn't possible on a car with only a single battery, as there is only one source of 12 volts. (I'm a low-voltage technician and I work with stuff that has multiple power sources where such a scenario is possible.) So yeah, back to the heat-related drawing board . . .
RonJon, that's an excellent troubleshooting idea. Bravo!