I have a 1999 chevy blazer that died and will not start

Question edited for clarity and fix typo.
Question moved to model category.

'Cranking' is purely the engine turning over. It cranks, almost starts and then it does nothing next time you turn the key? Flat battery.

Or, you turn the key, it cranks, fires and almost starts and then dies? More reasons for that scenario. Check for diagnostic trouble codes. Did you disconnect the battery when you replaced the fuel pump? Did it work after that? Does it have an engine immobilizer and did you reset it after the disconnect?

https://www.google.com/search?q=1999+Chevy+Blazer+crank+no+start

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Is there a chance that there is a light staying on in the glove box or under hood? Unhook the baterry cable and wire a bulb between
battery and cable. If bulb lights then start taking fuses out to find the circut that is drawing the current.

I saw what you replaced, didn't see any testing? What testing have you done? Make sure battery has a full charge?
When the problem is ongoing, have a helper crank it, while you check for spark at the plugs. If spark everywhere, use a gage and check proper fuel pressure. Also, check fuel injector pulse. Any applicable trouble codes?
If you have the spider fuel system, that system is noted for problems.

You may be having an intermittent failure with the fuel pressure regulator - checking the fuel pressure when the truck won't start may pinpoint this problem. If the pressure looks OK, this same problem can be caused by the ignition system as well (ignition coil or control module).

Check the plug wire from the ignition coil to the distributor cap.
If you haven't already, replace the distributor cap and rotor.
The GM Vortec's have issues with moisture getting inside the cap and rotor and causing problems.

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bad spark plugs, cam sensor or timing, or you could have clogged cat canverter

Yes, but there are at least a dozen other things that could also cause it. Fuel pump, ignition module, distributor cap, rotor, coil, fuel injector, fuel filter, blown fuses, broken wire or loose wires, etc.

THE FUEL PUMP IS BAD.

if your losing fuel pressure after the pump runs the drain back valve in the pump has failed.

and i doubt that you are seeing enough fuel pressure to run a vortec engine.

low fuel pressure equals a non running vortec

oil pump might be going bad

try messing with the radiator because it is most likely overheating