I have a 1996 chevy blazer replaced the fuel and

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

..

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.

seeing as you just changed the pump, can you hear the pump cycle when you first turn the key on? if not check all your plug in wire connections one my not have been in properly and came loose, hope this helps

try use this tool check your car.

Timing chain. It's probably broke!

You could try changeing the fuel filter its located under the drivers door mounted to the frame in the fuel line . But the most likely thing that it could be is the fuel pump. You could check fuse # 9 its a 20 AMP in the fuse box that feeds the relay located in the glove box but on this vehicle even if the relay wore bad the vehicle would still start it would just crank for a longer time . the fuel pump has a beck up power supply also feed from fuse #9 that runs through the oil pressure sending unit. So if its not the fuse its the pump or a bad connection at the pump and that is located inside the fuel tank witch needs to be droped to replace the fuel pumpGood luck with it but this is a common issue with blazers

lines may be clooged. I would disconnect the fuel line and cranck the engine and make sure fuel is reaching to the engine.

underhood relay center has fuel pump fuse

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/thomas_c50676e836a18949

Try to start it by cranking the engine for just a second (1) then turn ignition off, then again and if it starts on the third or fourth time you might look at the ignition switch behind your steering wheel. If you have an after market alarm you may want to make sure they did not tie into the ignition harness for the alarm during install, (very common) they cut into it then shove it under the dash. Hope this helps.

have the computer checked out. may need reprogramming and have updates added. also check for loose or corroded connections at the terminals.