What IT is 94 s10 Blazer LT 4.3 CPI Vortec (yes I,m sure). What IT is doing. IT will not start hot or cold. But if I prime it with gas into the pleum it starts right up and will run and drive untill I shut it off. Then it will only start if primed. NO prime no start. Prime it and it starts and runs. Also I get no codes throwen while it runs. Any thoughts?

 

check the fuel pressure guage? possibility

 

The fuel pump is probably supplying enough pressure to keep the engine running, but not enough to get it started.