Check valve

I have a c15 accert I was told I need to change the check valve in the back of the head, and I’m not wonder how do I go about locating it and what’s exactly do it look like?

 

To the best of my knowledge there is no check valve in the head. It's in the FUEL Filter housing.

 

Google cat filter housing pictures

 

Someone was talking about this a week or so ago,kept loosing prime.Someone else said there may be 2 check valves in the fuel system.