Hi, on my fuel filter housing the return line fitting next to the schrader valve is where I was told to put a clear hose to watch for air bubbles. I removed the fitting and I believe it is supposed to be a check valve isn't it ? mine seams to flow both directions, if anyone can verify this info and let me know where to get a new fitting let me know. thanks. also, I haven't been able to find any clear fuel line at stores. what did you use?