after 2 weeks of working on it still wont start. Checked the timing and its fine. Replaced the crank timing sensor. Replaced the plugs because they were fouled and over spaced. replaced Coil and engine control module, replaced the ignition switch also. After all that it is now trying to start but is backfiring and dieing.

 

sounds like maybe a fueling issue, maybe try changing the fuel filter if you hear the pump still trying to work. Or take the filter out all together and prime the pump to see if the pump is working at all?

 

follow this

https://blazerforum.com/forum/tech-a...agnosis-23038/

thats the best way to diagnose the fuel system