A mechanical fuel pump uses engine rotation, typically from a camshaft, to create pressure and draw fuel from the tank to the carburetor.
A mechanical fuel pump is a type of pump often found on older vehicles with carburetors. It operates based on the mechanical motion of the engine itself, rather than relying on electrical power like modern fuel pumps.
Powering the Pump
The action of a mechanical fuel pump drives through a camshaft or a specific shaft that rotates. This rotating shaft has an eccentric lobe (an off-center section) or a pushrod that interacts with the pump's lever arm.
As the shaft rotates, the lobe or pushrod goes under the pivot level and pushing the shaft up at one end. This motion causes the other end of the pump's lever arm to move, which in turn operates a diaphragm inside the pump.
The Pumping Action
The movement of the lever arm pulls the diaphragm downwards. This creates a vacuum within the pump chamber, drawing fuel from the fuel tank through an inlet valve.
As the camshaft continues to rotate, the lobe or pushrod moves away, allowing a spring to push the diaphragm back upwards. This upward movement pressurizes the fuel within the chamber.
The pressurized fuel is then pushed out through an outlet valve towards the carburetor.
Key components and actions:
- Lever Arm: Activated by the engine's rotating shaft or camshaft.
- Diaphragm: Moves up and down inside the pump chamber, creating suction and pressure.
- Inlet Check Valve: Allows fuel to enter the pump chamber during the suction stroke but prevents it from flowing back towards the tank.
- Outlet Check Valve: Allows fuel to exit the pump chamber during the pressure stroke but prevents fuel from the carburetor from returning into the pump.
The reference highlights that gasoline cannot be returned from the 1st check valve, ensuring a unidirectional flow from the tank. The fuel then drains into the carburetor through another valve, referring to the outlet check valve. This constant pumping action ensures a steady supply of fuel to the carburetor as needed by the engine.
