6X4 diesel Gator fuel bleeder pump

Changed the fuel filter on my 2001 6X4 diesel and when I tried to prime the filter bowl, the manual pumping lever did nothing. I took off the filter bowl, and there was no fuel flowing when trying to prime. Never had this problem before. The fuel tank is full. I then filled the bowl with fuel and remounted it. I started it up, and it ran and stalled, and on the second try it ran fine. I'm just wondering why the primer wouldn't work. Since it runs fine, I guess I shouldn't be worried, but then again, maybe something is amiss??

The repair manual says there is a second shutoff at the tank, but if there is, it's not obvious. Is there a screen or filter in the tank?

Any advice or explanations welcome.

Thanks.