90 chevy 350 with TBI starts but wont sta...

Barring any ignition problems, it may be one of these sensors that are part of the TBI.
TPS throttle position sensor, and the IAC idle air control
the following web page has some good info
http://www.goingfaster.com/spo/tbi.html.

id check the injectors and check idle speed and timing

I have a 90 chevy k1500 350 tbi with same problem! I have traced problem to... after turning on key fuel pump kicks on when u crank it over injectors shoot gas and truck starts! After few seconds injectors stop spraying and truck dies! This can happen many times over and over! Eventually sometimes truck stays running and all is great! I changed ignition module, oil pressure sending unit (which i was told controls gas after vehicle is running) fuel filter, computer, fuel pump relay, I am at a loss now! Hope this helps and hope someone can help me!

re check fuel pump connections and fuel pressure the pump even though new may b defective if pressure is good check ign coils

ign coil