UEL FILTERS TODAY APPEAR SIGNIFICANTLY DIFFERENT from
those used in the past, but their purpose remains the
same: to protect the fuel system by removing contaminants
such as rust, dirt and other foreign matter
from the fuel. Stricter emissions legislation, higher
injection pressures and ultra-low sulfur and biodiesel
fuels have all contributed to the evolution of fuel system
technology. The fuel filter is often overlooked in terms
of regular maintenance.
Purpose of Fuel Filters
Internal combustion engines consume a mixture of fuel
and air to produce energy. The most commonly used
fuels are gasoline and diesel fuel.
Older gasoline engines use a carburetor that mixes
the fuel and air in exact proportions for efficient carburetion.
It has many small passageways and delicate
parts which can be damaged by dirt. A dirty carburetor
can cause erratic performance or complete engine
Carbureted engines have been
replaced with electronic fuel injection
(EFI) systems. Fuel injection
is a much simpler, more precise
way to deliver fuel to the
Gasoline and diesel engines
normally use a fuel injector for
each cylinder. The injector meters
the fuel under high pressure through
small openings in the tip and into the
combustion chamber. A supply pump supplies fuel to
each injector. High operating pressures and tight clearances
make the injectors vulnerable to damage and
wear when exposed to dirt and contaminants. The key
to keeping a fuel system operating at its best is cleanliness.
Types and Sources of Contaminants
Contaminants may enter the fuel system when unfiltered
fuel is pumped into the vehicle tank or through
loose tank caps or faulty sealing gaskets. Fuel can also
be compromised by contaminants or dirt particles left
in the tanks or lines during the manufacturing and
assembly process. The most common contaminants
found in fuel are rust, dirt and water.
Rust usually comes from large storage tanks, but can
also form in vehicle tanks if low fuel levels are left in the
tanks over long periods of time. Rust is an abrasive and
causes damage to the injection system components.
The most common source for water is condensation
in the fuel tank. If the fuel tank is not kept filled, warm
moisture-laden air condenses on the cooler inside
metal wall of the fuel tank. Water can also enter the fuel
in underground storage tanks, during vehicle tank filling
on wet, rainy days, or through leakage past fuel tank
filler caps and improperly-designed vent openings.
Dirt can find its way into the fuel through dirty caps,
tank spouts and dispensing nozzles. Vent systems,
tank caps and other seals should be checked frequently
to ensure they are in good condition and none are missing.
Another contaminant sometimes found in diesel
fuel is bacteria.
Types of Fuel Filters
There are numerous types of fuel filters for gasoline and
diesel applications, including in-line, element/cartridge
In-line filters are located in the fuel line between the
tank and injectors or carburetors.
Element/cartridge filters require installation into
some type of housing in the vehicle fuel system. These
filters are often neglected due to lack of consumer
knowledge of the location and the inaccessibility of the
Spin-on fuel filters are similar to oil filters. They are
easy to replace and come in a variety of sizes.
Some automobiles and light trucks have two fuel
filters. The first filter, usually located in the fuel tank,
can be made of fine woven fabric or other filter
mediums. This filter prevents large pieces of
contaminant from damaging
the fuel pump. The tank filter
also prevents most water
from going to the engine.
Under normal conditions,
the tank filter will not require service
or replacement, however the second
filter requires regular service.
Gasoline and diesel engines are very
sensitive and will not tolerate dirty fuel. The most
delicate part of a diesel engine is the fuel injection
system. Injectors have moving parts with very close
tolerances, and small particles of contaminant can
damage them or cause erratic performance.
Servicing Fuel Filters
Fuel filters should be changed at intervals recommended
by the engine or equipment manufacturer.
When operating under more adverse conditions or with
very dirty fuel, the filters may need to be changed more
frequently. Replacing fuel filters at the recommended
intervals is the best assurance against engine problems
and fuel starvation.
Filters Available From AMSOIL
AMSOIL currently offers a full line of fuel filters from
WIX, Mann-Filter and Donaldson.