Mechanical Fuel Pumps
Are generally mounted on the outside of the Engine Block or Cylinder Head, close to the Crankshaft or Camshaft, which normally actuates the pump.
It is only used on carburetor cars as the delivery pressure required is not high enough for modern fuel injection systems.
Electrical Fuel Pumps
Are mounted outside on the car’s body, the undercarriage or under the hood.
Most modern car’s Electric Fuel Pumps are mounted inside the Fuel Tank and are known as Submersible or in tank Electric Fuel Pumps.
Why are fuel pumps needed in cars?
Fuel is needed to enable a car’s engine to operate, a fuel pump is needed to transfer the fuel from the tank to the engine.
To achieve this, fuel must be pumped at high pressure to pass through various components (Fuel Filter, Pressure Regulator, Fuel Injectors etc.) to reach the combustion chambers where it is burnt and converted to energy, allowing the internal combustion engine to run.
How It Works
The lever of the pump attached to the diaphragm is activated by an eccentric lobe on the shaft which the pump is connected to, this creates a pressure, pulling the fuel from the tank to the upper chamber of the pump, at this stage the outlet valve is closed sealing the pump chamber.
When the chamber is filled the inlet valve is sealed and the outlet valve is opened allowing the fuel to be pumped to the carburetor, this cycle is repetitive while the engine is turned on.
A return system is incorporated into the pump to allow excess fuel to be returned to the fuel tank, this is incorporated in both mechanical and electric pump fuel systems.
Electric Fuel Pump
Works on principle just as the mechanical fuel pump with a few differences, instead of and eccentric lobe, the Electric Fuel Pump uses a disc like turbine impeller, driven by an electrical motor, rotating at a high speed to suck the fuel to the pump and push it to the injector system, allowing for much higher delivery pressure.
Both Pumps incorporate one way check valves, to seal the pump’s fuel chambers alternately in an open and closed position.
In closing, a Fuel Pump is necessary in an Internal Combustion Engine, to keep a car’s wheels rolling.
Which do you prefer, Mechanical or Electrical ?.Let us know in the comments below.