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Technical Reference

Engine Components Need wear area can be the fuel injector needle seat. The
Protection needle mates to a seat which is the sealing surface to
control the flow of fuel to the combustion chamber.
If a particle becomes trapped between the needle
Engine liquid circuits (lube, fuel and coolant) are
designed in all shapes and sizes, both simple and and seat it can hold the needle open. In addition this
complex in design, and they all need protection particle and can the surface to become irregular and
from damaging contamination. Abrasive particles disable the sealing function of the needle. This can
enter the system and, if unfiltered; damage impact the fuel delivery performance of the injector.
sensitive components like pumps, bearings and
injectors. It is the job of the filter to remove these
particles from the fluid flow to help prevent
premature component wear and system failure. As
the sophistication of engine systems increases, the
need for reliable filtration protection becomes ever
more critical.

How Contamination Damages
Precision Parts Close-up of work fuel injector needle seat.
This cutaway
view of a
simple oil valve
ENGINE LIQUID FILTRATION TECHNICAL REFERENCE
illustrates how
particles damage Types of Contaminant
components. In Many different types of contamination may be
normal operation, present in engine fluids, causing various problems.
the spool slides Some are:
back and forth in the valve body, diverting oil to
one side of the valve or the other. This type of • Particulate (dust, dirt, sand, rust, fibers, elastomers,
value is typical in engine oil control circuits. If a paint chips)
particle lodges between the spool and valve body, • Wear metals, silicon, and excessive additives
it will erode small flakes from the metal surfaces. (aluminum, chromium copper, iron, lead, tin, silicon,
As these flakes are moved back and forth by the sodium, zinc, barium, phosphorous)
action of the spool, they can roll into a burr that • Water
jams the spool and disables the valve. • Sealant (Teflon®* tape, pastes)
• Sludge, oxidation, and other corrosion products
In these pictures we see examples of how • Acids and other chemicals
contamination can impact fuel injectors. Fuel • Biological, microbes
injector nozzles are small passages that deliver
an evenly distributed fine mist of fuel to the
combustion chamber. These fine passages can
become plugged with contamination. Another

Close up of new (left) and worn (right) fuel injector nozzles.

106 • Engine Liquid Filtration www.donaldson.com