Fuel pumps use the principle that liquid under high pressure automatically flows to areas of lower pressure. This means that a fuel pump needs to be flowing before it starts pumping on its own; if the pressure in the starting area is too low in relation to the pressure in the receiving area, then nothing will happen as there will not be enough force. This is what priming is for. It is a kick-start to the fuel to change its pressure and make it start flowing on its own.
Compress the attached squeeze bulb if there is one. The squeeze bulb is designed for priming by pushing fuel one way down the pipe but not allowing it to flow the other way. If you press the bulb a few times, fuel should go through the system and start flowing on its own once you start the engine.
Attach a manual pump, taking care to close the fuel supply line before you do so. Manual pumps are necessary on larger fuel pump systems that require more fuel than a squeeze bulb can handle.
Press the manual pump a few times until fuel is running through the system.
Remove the pump and reattach the fuel lines. The fuel pumping system should work on its own now.