FUEL FILTRATION: Part II .. continued
written by: Harry Lewellyn
|
This article is a reprint from the Bonus Issue of FOURWHEELING ACADEMY.
The FOURWHEELING ACADEMY is a regular part of the "Ecological 4Wheeling
Adventures" Newsletter.
|
PLEATED PAPER FILTERS |
Figure 1-a
Typical canister type pleated paper fuel filter.
|
An efficient surface filter must maximize
surface area without unduly increasing filter size. A simple flat surface filter would clog too
fast. You want as much filter in as small a package as possible. This is accomplished with arched
pleats [Figure 1-a].
The construction is pretty straightforward. You wrap a pleated paper filter element around an
inner perforated or expanded metal support structure [Figure 1-b]. This is
sealed at both ends, one allowing fuel flow between the inside of the support structure [Figure 1-c]
and the outside. You encapsulate this in a metal can with another
tube from the outside of the paper element to the fuel tank. E is a protective transport cover I
use on both C and D.
Dirty fuel flows in via D. The filtration element (A) cleans the fuel, and contamination-free
gasoline flows to the injectors through tube C.
|
Figure 1-b
|
Figure 1-c
|
FILTER DIAGNOSIS
|
With the Explorer problem above,
I had ample opportunity to scrutinize several clogged filters before I found the problem. First
indication of fuel starvation was lack of power accelerating uphill at highway speeds. The [Figure 1-c] show the pleats, both clean X and dirty Y. Note the dark dirt on the
contaminated side of the paper. I was continually amazed how the car could run on a filter that I
could not blow through!
|
FILTER REPLACEMENT SAFETY 5, 6, 7
|
Think safety! First and foremost,
understand EFI systems run at high pressure — 30 to 60 PSI. This "pressure charge"
is stored even after the system is shut down. You must be prepared for fuel to forcefully squirt
out creating a personal or fire hazard. Maybe both! This means you must either relieve the
pressure at the fuel rail test point or be prepared to wrap the first disconnect point with a rag.
Your shop manual may offer other pressure relief techniques. Here are the one, two, threes of fuel
filter replacement safety.
|
- Follow your manufacturer's recommended replacement procedure.
- When at home, and when possible in the field, let the system cool.
- Wear glasses. Be prepared for the initial squirt of gasoline per above.
- Be careful of hot and sharp objects.
- Ensure the vehicle will not roll or move due to unstable ground.
- Use safety stands under the frame if you must elevate the vehicle.
- Clean all dirt from around the connections.
- Do not run the engine while changing the filter. Provide adequate ventilation for the final
leak test.
- Keep a fire extinguisher handy and caution onlookers about the gasoline fire hazard
(smoking).
|
FUEL FILTRATION : : [ PAGE 1 ] : :
[ PAGE 3 ]
STILL CONFUSED? CHECK OUT [ EFI 101 ]
|
About the Author
|
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.
|