Power And Performance II Practice Test

Fuel delivery to a carburetor in older engine setups is accomplished by a pump that is physically driven by the engine. A mechanical fuel pump is usually camshaft–driven, using a diaphragm to pull fuel from the tank and push it toward the carburetor, keeping a steady flow and pressure as the engine runs. The float, in contrast, lives inside the carburetor’s fuel bowl and rises or falls with the fuel level to open or close the needle valve, maintaining the correct level rather than supplying fuel. The throttle linkage controls the opening of the throttle plate to regulate air intake (and, by extension, the mixture), but it does not move fuel itself. Electric fuel pumps perform the fuel delivery but are powered electrically rather than driven by the engine’s mechanical motion. So the component that is mechanically driven to provide fuel to the carburetor is the mechanical fuel pump.