P0171 2006 Chevrolet Trail Blazer -

Question

1995 chevy blazer 4.3 v-6. will not start. reading is negative 100% short term fuel trim. have changed most sensors, cleaned everything. changed crank sensor, cam sensor, O2 sensors, etc. does not show trouble codes, only the -100% short term fuel trim. starting to look like a good fish habitat.

Answer 1

p0171 means there is too much are air and not enough fuel 

could be a bad fuel pump, intake leak and so on (diagnostic procedures are below)

check fuel pressure first