1995 Chevy Blazer fuel

I have a 1995 blazer with 200000 miles some times it starts right up and some times I have crank it over and over once in the while it starts for a second and stalls out when it dose start it wont take the gas I have to be vary gentle with the gas peddle or it will stall out and then maybe it will start or not I put the fuel pressure gauge on it and it has 50 / 55psi but as soon as I stop turning it over the pressure drops down to 0 right away and when it starts like I said as long as im easy with the gas peddle I can drive it for hours and it runs fine has anyone out thare had this problem befour if you could help I would love to hear from you thankz for taking the time to read my problems mark from st catharines ontario