Slanted blades on the rotating impeller push the water the way the blades on an electric fan push air. A mechanical fuel pump is driven by the camshaft or by a special shaft driven by the crankshaft.

Gasoline Pump Wikipedia

As the shaft turns a cam passes under a pivoted lever and forces it up at one end.

How does a gas pump work. This is done with an auxiliary sensing tube running from just inside the mouth of the nozzle to a venturi pump in the pump handle. The other end of the lever which is linked loosely to a rubber diaphragm forming the floor of a chamber in the pump goes down and pulls the diaphragm with it. The more gas goes in the more air must come out explains jake.

Most modern pumps have an automatic cut off feature that stops the flow when the tank is full. A mechanical valve in the pump handle detects a change of pressure and closes preventing the flow of fuel. A pipe is inserted in the water.

A submersible pump as its name implies is submerged below the surface of the liquid where it uses a propellerlike device called an impeller to move the fuel upward. A suction pump moves the gas using the principle of unequal pressure. When you fill your tank with gas you re replacing the air that s in there.

Well it has to do with the way the gas pump works.