I assume you are talking about an electric fuel pump
like I have on my YSE8. Is the pump
running when the ignition is on? Are any fuel
valves between the tank and pump
closed? Is the vent on the fuel
tank restricted in any way? How are the filters? There is usually 2, a Racor or similar and the smaller one on the engine itself. Is the fuel
in the tank clean? Follow the route from tank to injector and check everything, make sure the connections are tight and that air isn't getting in anywhere.