Fuel pump not pumping but its a little wierd? ?

ok i just rebuilt the motor in my 86 firebid 2.8 5 speed. i go to start it the first time after rebuild, doesn't fire. check everything and find no fuel to be the problem, so go to the back listen for the pump- nothing, so i pull it,test and replace. (the pump was fine a month and a half ago) try again nothing but i get voltage when i turn the key to crank but nothin when just on. i tested the pump with a extra bat and jug of gas - works. can you help ??