How does it work?
In some
installations
the
filter system has automatic water detection sensor; when
the maximum acceptable water level in the filter
is
reached,
a control lamp on
the
dashboard starts blinking. To reduce the possibility of forming
condens water in the fuel tank, we advise, to fill
the
tank
at the end of the day or
week
to
the maximum, reducing the free airspace above the fuel. The
less air in the tank, the less water vapour that
can
condense.
For wintertime, the fuel suppliers
provide
'winter diesel'. A certain amount of additives has been added
to the diesel fuel to reduce the possibility
for
the
paraffin in the fuel to crystallise (flocculation).
This
flocculation happens at temperatures below -20C or even above
-20C because of wind-chill factors.
In
certain
filters a heating element
with
thermostat is present, thus avoiding flocculation temperatures.
Once
severe flocculation has occurred, all filters
must
be replaced and
the
fuel lines must be cleaned. The filter element retains particles
above
5 to 10 microns.
There are three types of fuel systems:
 |
carburettor
systems |
|
fuel injection systems |
|
fuel system for diesel engines |
Carburettor systems
In carburettor systems the fuel pump aspirates the fuel from
the fuel
tank
and pumps
it in the carburettor. An 'in-line' filter is situated in the
line
between
tank
and carburettor
to prevent
that contaminants in the fuel plug the nozzles in the carburettor.
The consequence of plugged
nozzles
is that
the engine
stutters or stops
altogether.
The in-line filter is a small filter element in nylon housing;
the filtration quality is
20 microns.
The filter
housing
has connecting pipes
to the
fuel line. The nylon housing is transparent so that serious
contamination can be observed.
The in-line
filter
must
be replaced in accordance with
the instructions
of the manufacturer.
Fuel Injection systems
The components
of injection
systems are much more sensitive to contamination than carburettor
systems. Therefore these systems always have
a fuel
filter, either
an in-tank
or an in-line filter. The fuel pump, usually mounted in the
fuel tank, aspirates the fuel in the tank and pumps
it via
the filter element to the injectors.
The filter
element is finer than the carburettor system: 5 to 7 microns.
The element is mounted in a metal housing and
also
absorbs the water in the
fuel.
The metal housing is usually mounted at the underside of the
car; therefore the housing must resist salt spray.
Fuel system for diesel engines
The diesel
fuel
is aspirated by the fuel pump and is pumped to the high-pressure
injection
pump via a fine-filter. The cylinders of the injection system
are
manufactured
with
a very high precision, having tolerances of 2 to 5 microns
because of the very high pressure (up to 1800 bar) in the
injection
system. It is evident
that
the life of the injection components is negatively affected
by abrasive
particles as well as water in the diesel fuel (acidity, corrosion)
resulting
in:
|
irregular burning
of the fuel |
|
higher fuel consumption |
|
less engine power
|
|
difficult starting |
At the bottom of the fuel pump, a filter is mounted to retain larger
contaminants. The filter element is mounted in a transparent housing that also
serves as water separator. Because the specific weight of water is higher than
diesel fuel, the water is visible at the bottom of the transparent housing. It
needs to be drained according the guidelines. The finer filtration takes place
in a 'duplex' filter where 2 filter elements, one for larger particles and 1
for particles down to 2 microns, take care of the fine-filtration.
The filters for diesel fuel are usually located at the highest point of the
installation; therefore they can collect air bubbles which prevent the pumping
of the diesel fuel through the system. To remedy this, a little bolt at the top
of the filter can be unscrewed to allow the air-bubble to escape. |