help please help

i have a 90 anniversary mustang,recently it quit cranking and i noticed
that normally when you turn the ignition switch on the fuel pump will cut
on long enough to spray through the injectors but now it constantly runs
with the switch on but i think im getting fuel caus i can release the fuel
from the relief valve so i know im getting gas and i have spark but
whatever is causing the fuel pump to run costantly is causing it not to
crank please help im trying not to think its the pump cause im getting gas
but it also sounds like air going through my fuel rails on the intake