That little valve in the pump I'm talking about just stops the fuel from dropping back once your fuel pressure is back the engine will run no problem .??? I ask a fitter that I know he said---- It may be something as simple as moisture in the fuel or a problem with the fuel filter so I would recommend the fuel filter is changed now if there is any doubt its not been done for a while. ??? I suspect there may be a fuel pump problem, although it may just be a sensor which is cutting the fuel supply or not reading correctly such as a rail pressure sensor or return valve.????the fuel is being allowed to get air in it or is running back to the tank. We cannot rule out a sensor with this but its more likely to be on the fuel system, the fuel filter would be the first step. Frank