Truck broken? NEED HELP?

pickup truck 2000 chevy will start and idle, 55psi at fuel rail, when load is applied dies out runs lean on the pressure tester on the fuel rail I pushed release valve let what seemed like air out of the line then it runs fine but when I take the tester off and cap the fuel line and let it sit for a while i turn it back on and it will not take fuel again i am not sure if i am getting good flow could the fuel pump be weak i changed the fuel filter wondering what could be wrong could it just be bad gas maybe confused need help!