I just put a new 350 motor in a 1985 chevy c10. I've had no problems with anything until I've tried to crank the truck. When I start the truck it will run great as long as I keep pouring fuel in the carb. As soon as I stop the motor dies. I've pulled the fuel line off and replace the carb fuel filter. I've also turned the motor over with the line off and I get fuel coming out the line. The only thing that raises a red flag that I'm seeing is when I'm turning the motor over with the fuel line unhooked it's not a steady flow of fuel..it's consistent spurts of fuel..I don't know if that's normal or not. Please reply if you have any advice

 

Has it had a carb-kit lately? Sometimes after an extended crank, I'll take the air-horn off the carb, see if there is any gas in the float-bowl.

I think the pressure rating for a mechanical pump is 7-9 PSI.
Can you measure the volumn, output, without getting the starter hot?