I have a 98 chevy blazer 4.3 4 door 2 wheel drive,I started my truck to go to work as usual as I was going down the driveway it stalled,I tried to crank it back up,but it just turns over and will not start,I can hear the fuel pump working and there is gas coming out of the valve under the hood when you push it with a scewdriver,so I'm sure it's not a fuel problem,I deliver mail with this truck it ran fine the day before,but ever so often something pops in the motor,I'm not sure if this could be related to this problem,I checked all relays in the box they are all clicking when turning key on,I would appreciate any help,my truck is at the bottom of a hill in my drive,lol

 

Fuel from the schraeder valve is definitely not a sign of sufficient fuel pressure for starting. Please read these threads:
98+ No-Start - Engine Cranks OK

96+ Fuel System Diagnosis