Blazer engine dies after driving for a while when it is hot outside. I let it sit for 30 mins and it starts. had the thermostat changed, not it. Fuel pump changed, not it. No one can find the problem. Help

Did you change crankshaft sensor?...camshaft sensor,fuel filter.

It sounds like your fuel pump overheats

Did you check the coolant temperature sensor if it thinks the engine is overheating it will shut the engine down.

Check for fuel pressure and check for spark during the no start condition. Also check the crank sensor, it is located behind the crank pulley mounted in the engine block on the 4.3 L engine
I hope this helps.

What does it do, if you try to accelerate when this starts to happen? If it dies,sputters or is sluggish, I'd start by changing fuel filter, and if that doesn't help, have fuel pressure tested when (if at all possible) this begins to happen. Had similar problem, winter was fine, hot weather it would die, and restart after 20 minutes or so, then go a fair distance again, then same thing. Fuel pump was on it's way out and when it got hot, fuel pressure would drop. First thing in the morning when fuel in tank and pump was cool, ran like a charm, but on way home from work, after sitting on a hot day, fuel got warm/hot, and pump heated up and that's when it started. Carried a fuel pressure gauge with me. Fuel pressure when cool, was 49 psi, and when it got hot, eventually dropped off to 2 psi. Sat for 20 minutes, jumped back up to 49psi, took off for home,then would eventually get lower and die again. Changed pump and filter, all was well. Try filter first, you have nothing to lose, and it should be changed if pump replaced later anyway.

On some models, the Engine Control unit has a power supply relay. These relays some times get internal dry solder points. After driving for some time the the solder will get hot and separate. When it cools down it makes contact again. You will have to replace this relay or open it up and re- solder the solder joints. The relay is usually located on the main relay station in position 3. the relay station is located behind the right dash panel.[right hand drive vehicles]. You may need to refer to a manual for your specific model to find the exact location of the relay.

sounds like the new fuel pump sucked dirty gas out of the tank try changing the fuel filter and put some fuel injector cleaner in the tank, also check the fuel line it may be bent from changing the fuel pump

Have you check the O2 sensors? How baout cleaning the MAF and Throttle body? Thermostat?

How does the temp gauge look whn it stalls?

How much fuel pressure?