Fuel Pumps-101

Fuel Pumps-101

What is a Fuel Pump ?

A Fuel Pump is a component generally used in internal combustion engined cars, it’s function is to pump fuel (it could be Petrol, Diesel or any other combustible fuel.), from the fuel tank to the engine, 

Fuel Pumps are divided into two types,

  • Mechanical
  • Electrical
Mechanical Fuel Pumps

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.

In Tank/Submersible Electric Fuel Pumps

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.

Outside mounted 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

Mechanical Fuel Pump

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.

A Mechanical Fuel Pump
How Fuel flows from the Tank to the Engine
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.


An Electric Fuel Pump
A Submersible/In Tank Electric Fuel Pump
A outside mounted Electric Fuel Pump

In closing, a Fuel Pump is necessary in an Internal Combustion Engine, to keep a car’s wheels rolling.

#great deals on fuel pumps

Which do you prefer, Mechanical or Electrical ?.Let us know in the comments below.

Until Next Time “Safe Motoring”

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About Me

Gary De La Cruz

I have been 30+ years in the motor industry, still hands on, and have great passion for my chosen profession, I learn new things each day and believe that "if you enjoy your work, you never have to work a day in your life"I believe in honesty, integrity and helping where help is needed.

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