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FUEL FILTRATION 101
written by: "Silver Coyote" Harry Lewellyn
Fuel Filtration 201 covers Fuel Filtration in depth.
The FOURWHEELING ACADEMY is a regular part of the "Ecological
4Wheeling Adventures" Newsletter.
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15 MPG
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Here's a fascinating way to
look at fuel delivery. At 15 MPG, the vehicle has to s-t-r-e-t-c-h one gallon of fuel over 15
miles. If that were a pipe-like container, it would be 15 miles long and about 30 percent smaller
than the diameter of a stickpin! And considering the fuel pulses, it's smaller than that!
Clean fuel is important, and even more so for electronic fuel injection (EFI).
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EFI CLEANLINESS
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With the introduction of gasoline fuel injection around
1950 came the need for cleaner fuel. By 1990, all cars sold in the USA had EFI of one sort or
another¹. Fuel injection means a cleaner environment, more power and better
fuel economy, but EFI demands very clean fuel. The tiny fuel delivery holes in each injector are
about one-third to one half the size of the dot over this i². As you can
imagine, that's easily clogged.
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HOW CONTAMINATION ENTERS
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- Contamination enters the fuel system four ways³.
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- The fuel you put into the 4X tank may be dirty or "wet." It's not
uncommon for water to accumulate in underground filling station tanks. Your spare fuel container
may be contaminated with rust and dirt, too.
- Dirt may also enter the 4X tank directly via a bad filler spout cap or vent
connections.
- Further, the tank and lines may "create" metal oxides (rust or
aluminum oxide).
- Finally, contaminants and dirt may be left in the tank or lines at time of
manufacture.
I have personally experienced and traced fuel
filter problems to all but the last one.
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4X FUEL FILTRATION
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Most vehicles have two fuel filters: one in
the tank and another in the delivery line. The tank filter is almost never replaced. It is
designed to stop large particles that would damage the fuel pump and prevent water from entering
the balance of the system. The second, inline filter is the engine's primary line of defense
against dirty fuel. Your manufacturer recommends how often to replace this most critical system
component.
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CONTAMINANT DAMAGE
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Dirty fuel can damage an engine in three
ways. Least likely is direct pump or injector damage. More likely is injector clogging. These are
explained in the second part. Most likely is "sanding" of
engine parts like the valves, valve guides, pistons and cylinder walls. Both aluminum and iron
oxides can form in the vehicle's fuel tank and lines, and are powerful abrasives. I'm not
an anti-plastic guy, particularly when it comes to fuel storage. Plastic tanks cannot contribute
contamination to the fuel, and stainless steel is even better.
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ENSURE CLEAN FUEL
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I'm far from an oil change fanatic, but
fuel filter replacement is high on my maintenance list. Part two offers hints and suggestions. It
ain't as easy as changing the toilet paper, but it's an invaluable skill when in the boonies.
REFERENCES
¹ www.howstuffworks.com/fuel-injection.htm
² RACOR Fuel Filtration brochure No. 7550
³ WIX filter Service Manual, www.wixfilters.com
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Author's Note
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This article first appeared in the November-December 2001 issue of
Ecological 4Wheeling Adventures newsletter.
With no reservations, I can tell you Trail Quest fuel tanks pass
strict "Coyote scrutiny" with flying colors. Stainless steel is as good as plastic regarding rust, but immeasurably stronger.
Vent fittings of the screw-in variety all but eliminate loose fitting contamination
entry, period. Add steel shields beneath stainless steel tanks with screw-in fittings and
you've got the best combination of contamination-free, bullet-proof, off
highway fuel container possible!
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About the Author
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Harry Lewellyn is the author of "SHIFTING into 4WD" and the
"California OHV Guidebook" produced by the state of California Department of Parks and
Recreation.
He leads 4WD trips throughout the US, Baja and mainland Mexico.
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