fuel pressure

changed fuel filter on 88 sub with 454 throttle body injected . when i took gas line loose there was no pressure on the system . truck was driven to parts store then let cool down (about an hour ) turned wrench expecting a little spray of gas and there was none . changed filter then truck was real hard to start just about ran battery dead . finaly started after repeated pouring a little gas into throttle body and try again. shouldnt there be pressure in system even when not running?