Breakdown: How fuel pumps work

25 June


What is it?


A fuel pump refers to the nozzle, pump, pipes, hoses and underground tank at a fuel station.

How does it work?

Whether it’s a pay-at-pump or standard fuel pump, once it is authorised, the pump’s motor will start. A car, van or motorbike will use a ‘low flow’ pump, delivering fuel at 40-50 litres/minute. A HGV uses high-speed diesel pumps, dishing out diesel out at 120-130 litres/minute. 

The fuel nozzle has a sensitive pressure detector that measures the pressure inside your vehicle’s fuel tank. When the tank pressure is higher than outside, the fuel cuts out. On a hot day, the nozzle will also cut out prematurely due to the higher pressure in your car's tank.

Why do we need it?

In the past, excess fuel vapour from the pump and tank was vented into the air, which was smelly, harmful to the environment and dangerous – fuel particles in the air made the area extremely flammable. Nowadays, vapour is kept in a separate, underground, tank through a vapour recovery system. This system syphons the vapour from the pump and your car while it pours in fuel.

Anything else?

The Government regulates fuel pumps under the Weights and Measures Act 1985. They pour out 20 litres into a measure, taking account of the temperature of the fuel, then let the fuel sit until the temperature has steadied to 15°C (UK standard fuel temperature (STA)). The change in fuel level is taken account of; it needs to be within the margin of allowable error – usually around 0.001%.

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