Fuel Line Check Valve

[zx_man]

:help I have a 82 Datsun ZX (non-Turbo) When I start the car First thing in the Mornings, I turn The Key, it fires off then acts like its running out of Gas, after 2nd cranking it usually starts and runs fine rest of day. I have been told the problem is the Check Valve coming out of the fuel pump. If I take it off and replace it after bleeding off the line pressure, do I need to drain the Gas tank to keep gas from commming out of the pump or will the pump itself prevent the gas from pouring out of the tank on the ground while I replace the Valve. Any remarks would be appreciated.. :ylsuper