The vehicle’s engine alone is nothing but a big air
compressor. It is not until we add the correct amount of fuel to the mix that we
will achieve a good combustion able to create enough power to move the car. The
only component pumping gasoline to the engine is the fuel pump.
Types of fuel pumps:
Early cars were equipped with mechanical pumps located on
the engine block. The most common mechanical pumps are made of a diaphragm and
a spring that are pushed by a metallic lever excited by the engine’s camshaft.
Therefore, the pumping frequency is proportional to the engine speed in this
type of fuel pumps.
Mechanical pumps were used with carburetors and later abandoned in the injector
era due to their low output pressure (less than 1 bar).
New cars have electric fuel pumps, they are mostly located
in the fuel tank and able to generate more than 10 times the pressure of a
mechanical pump.
This kind of fuel pumps are operated, most commonly, by a 12V two wires connector that feeds
the motor’s brushes which provide the electricity needed to rotate the armature
that is connected to the impeller. The impeller is responsible to pump the fuel
from its holes to the inside of the pump (passing through the armature/rotor
chamber) and to the top output neck of the fuel pump.
The newest technology in the market at the moment is
brushless fuel pumps which are electrically more efficient.
Electric fuel pump specifications:
Electric fuel pumps datasheets are very important, they
indicate the flow and pressure of the fuel vs the voltage and current fed, the
electric efficiency (which helps the customer to understand the amount of heat
generated as well), type of fuel that is able to handle, and the mechanical
valves distribution (One-way valves, check valves…).
These information are critical to understand the amount of fuel delivered to
the engine and the reliability of the pump.
The performance of the car is directly affected by the
efficiency of the fuel pump. When the fuel pump starts to die, it will consume
more current, the impeller will rotate with lower speed (a full rotation will
take more than 7 ms), thus it will deliver less fuel than expected.
Causes and symptoms:
A broken fuel pump can be caused by:
· Dirt and particles in the fuel: (Even small particles from the filter or the sealant might cause damage to the pump.
· Dry running the pump: The fuel lubricates and cools the pump; a dry run will lead to the destruction of the inner parts of the pump.
· High voltage and current feed: Burns and overheats electric components which results in short circuits.
· Time: Like any other component, the fuel pump has a lifespan that varies from a car/brand to another.
· Incorrect fuel type.
· Low fuel level: Low fuel level will increase the chances of the fuel pump getting dirt into its system or running dry for a short time in corners
A broken fuel pump will reduce the power and the fuel efficiency
of the engine while increasing the vehicle’s emissions. In addition, it might
affect the starting time, cause random bangs and stall the vehicle.
Conclusion:
The fuel pump is the main character when looking into the
vehicle’s power. It is the only component responsible for delivering fuel to
the injectors.
A fuel pump giving up can be diagnosed by a lack of performance, higher fuel
consumption and sveral mechanically noticed symptoms like bangs, vehicle stalls
and an increase in the starting time.
Numerous causes can kill a fuel pump. Mainly related to the electric voltage
fed, to the quality, type and quantity of the fuel that the fuel pump operates
usually in.
A fuel pump in general is not a maintenance part, it is
changed when it starts to fail, and should survive more than 100 000 miles.
