Bad priming pump? Squeeze bulb in the line works great.
I would second that. I also added a fuel line (and appropriate fuel valves) just before the Yanmar fuel pump. What this does is allow be to use the fuel bulb to hand pump fuel from the tank, through the racor filter and then (using the engine fuel return line) run the fuel back to the tank. This removes all air in the racor and all the fuel line up to the yanmar fuel pump. When these line are full, I shut the valve that allows the fuel to go to the yanmar fuel return hose. Now when I hand pump the yanmar fuel pump everything before the pump is primed and a few strokes of the pump start fuel flowing to the yanmar fuel filter (open bleed screw). This makes job easy. Good luck.