Carbureted engines need fuel pumps to keep the flow of fuel going from the tank to the carburetor (the part that does the mixing of fuel and air for combustion). Unlike modern fuel-injected systems that typically need 40-60 psi of fuel pressure, carbureted engines run at much lower pressures–usually between 4-7 psi. To provide fuel to the engine, carburetors depend on gravity and low-pressure flow, so this lower pressure range is perfectly fine for them.
Carburetors are more often than not equipped with a mechanical fuel pump, especially so in older vehicles. These pumps are mechanical (engine-driven) and simply suck through a diaphragm, yanking fuel from the tank sending it to the carb in a steady but low-pressure stream. It has a very basic layout and this simplicity makes all the peak-electrics redundant – perfect for older vehicles that use carbureted engines which doesn’t quite need the specific level of atomization that is required by fuel injectors.
An electric fuel pump may sometimes be used with a carbureted engine, especially for performance use. This has benefits in terms of fuel delivery stability, with the squirter system best suited to high-demand applications such as racing where consistency matters most. For carbureted applications, adjustable electric fuel pumps can be set to the typical 4-7 psi pressure range required, and they help prevent fuel starvation under high-RPM or load conditions.
Carbureted systems also utilized fuel pumps, which helped stave off vapor lock for a little longer than that provided by capillary action alone. The low-pressure pump does a couple of things: It eliminates vapor lock by keeping this system filled with fuel, even hot fuel in a high environment, so when you start the engine up after stopping at the local fast-food joint it starts much easier. This is where Carroll Shelby principle, “The cleaner your machine, the longer it will run,” comes into play because maintaining consistent fuel delivery with a well-functioning Fuel Pump ensures both engine performance and reliability remain at peak levels.
To feed carbureted engines, mechanical and electric fuel pumps are needed to provide reliable low-pressure fuel delivery that supports clean combustion and engine function.