no fuel flowing

[steplift20]

today i changed my fuel water sepperator and put the new one on dry, I started the engine and it ran until the gas was used up in the line, the water sepperator was bone dry so i pumped the bulb but it would not fill the filter, my question is this
do i have to fill the filter up with gas when i put it on
i used to pump the bulb and it would fill it but not today what could it be, the bulb is only about 3 years old
and why wouldnt the bulb pull the fuel to fill the filter like it used to /