I've used the search function and found a lot of variations on this problem. but none that seem to quite hit he nail on the head -
I have:
2001 Blazer 4 door 2WD with 4.3L engine, 254K miles on it.
I replaced the fuel pump about 18 months ago after it finally died.
It's been running fine ever since, but it has (very recently) quit starting when hot.
I can start it 1st thing in the morning & drive the 11 miles to work, no problem.
I can go out to lunch (2-5 mile radius) no problem.
But if I drive long enough for it to get hot enough it runs fine,
doesn't sputter, misfire or anything but when I shut it off it won't restart.

When I try to restart I don't hear the fuel pump do it's 2 second 'prime'.
I have to wait anywhere from 45 minutes to over an hour for it to cool down or
whatever it is that clears the problem, then it starts like normal.

I have opened the PCM and cleaned out/replaced the thermal paste where the 2 rows of ICs make contact with the housing,
I also (earlier today) did the same for the ICM, heatsink, and the heatsink mounting plate.
I drove it around a while today to heat it up, shut it off, and it wouldn't restart.
I hit the PCM and ICM with a blast from an upside-down can of computer dust remover to cool them off
but it still took about 30 minutes before it would restart.

I feel sure it's something relatively minor, some sensor overheating or
something because once it's cleared the engine starts and runs fine.

But it does make stopping at the grocery store on the way home from work take
a lot longer than I'd like it to.

Guidance/suggestions?

 

Have you checked the crank and cam sensors?

Josh

 

If your pump is not coming on sometimes then you need to check the power and ground to it. You did not mention what brand of pump was installed when it was replaced. You may also want to do a fuel pressure and leak down test.

 

Josh -
I haven't checked those, but it's not throwing any codes (at all) to indicate that.
I'd also expect if either (or both) of them were going flaky I'd have other problems,
like misses, rough idle, stalling. When it running, it runs smooth, plenty of power.

Burned -
I don't recall what brand the fuel pump is, I know it's not a Chevy or AC/Delco.
I've jumpered the fuel pump relay when it been in 'stall mode' and I can hear it run.
What I haven't tried yet (because I didn't know about it till cruising this great forum)
is to use the fuel pump prime terminal on the fuse block to see if that makes it do anything different.

I've tried to find out if there's a fuel pressure sensor somewhere (other than the fuel tank pressure sensor)
but so far apparently not.

 

Have you checked the fuel pump relay? Easiest way is to swap the relay out for a good relay usually found next to the suspect one. How about the fuel pressure regulator?

 

So I finally got to do fuel pressure & leakdown tests, when everything's cool (engine hasn't been running)
I get 64 psi when the pump's on and about 54 psi after 10 minutes.
I used one of these to do the test:
https://actron.com/content/fuel-pressure-tester-kit
(PS - It's on sale at NAPA right now)
Since the gauge is marked in 2-lb increments all the readings are approximate.

I ran it a while to get to 'restart failure' mode.
The 1st time I triggered the pump to prime manually at the fuse block and it worked.
I started up & drove around a little longer.

The 2nd time I tried it wouldn't prime manually, so it seems like either a bad connection at the fuel pump that craps out when it gets hot
or the fuel pump is overheating and shutting down, and it's time for another fuel pump.

Is there anything else between the priming point on the fuseblock and the pump?
any other sensor or thermocouple that would stop the fuel pump from operating?

 

Don't forget grounds

For an inop fuel pump, what is the fuel pressure when it won't start? If nothing, then check to see if FP relay is being energized by the PCM and has a good ground. If it is and does, then for the money and ease of install just go ahead and put a FP relay in it. If still no pressure, then fuel pump wiring, or FP ground.

AlldataDIY subscription has the wiring diagrams that you apparently need. With electrical, you simply have to have them.

If you need help with basic circuit troubleshooting, then let us know and we can help. You will need a test light and a multimeter to work on electrical problems.

Good luck,

Les

 

Sorry to be so late in updating this, but new fuel pump has solved the problem.

 

Thanks for letting us know.