Date: Sat, 27 Nov 1999 14:18:07 -0800
Reply-To: Doktor Tim <doktortim@ROCKISLAND.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Doktor Tim <doktortim@ROCKISLAND.COM>
Subject: Re: Contaminated fuel was Re: How does the Oxy Sensor Work/ go
bad?
Content-Type: text/plain; charset="us-ascii"
At 11:17 AM 11/27/1999 -0800 you wrote:
>I really want to understand if having a vented fuel system, with a fuel
tank in the slipstream, >can produce condensate inside the fuel tank. I've
read many posts with the "clogged" fuel >filter, power surging etc. My
guess is that it is really water in the fuel filter that it the >problem
with surging, no starts and etc. in some vans.
Agree, and if said owner's would always record the date/milage of filter
replacement, they can determine if life expectancy is reasonable, or if an
anomaly associated with type of use is reducing effective life.
>Is the vanagon's fuel tank up front, possibly more exposed to the wind
slipstream, becoming >super cooled, i.e. colder inside the tank than
outside air. This would cause the the air >temperature inside the fuel
tank to become lower to the point at which moisture in air will >condense
from water vapor to water droplets.
>Simply put, conditions conducive to "rain" in the gas tank can occur at in
high humidity low >temperature situations.
Those plastic tanks put off far less condensation than a metal one will due
to much lower thermal transfer. In any case, if you are the type to "bottom
up" with reserve indicated fills of $10 every day or two, the consistant
low level or gas to high level of air in the tank will greatly increase the
vaporized water available for condesation. This would be one reason more
than normal amounts of condensed water would find the bottom of the tank.
>Perhaps this is why the fuel filter on our van is located horizontal and
so large? Maybe this >was a cheaper fix/ solution in "most" operating
conditions, that to put a non-vented fuel >system in the van.
The choice between vented and non vented systems is a choice of lesser
evils in the mind of the designers. Plastic tanks don't hold up to pressure
over the long term as well as steel unless it is VERY HIGH spec High Cost
structual matrix plastic, when two big flat sides are present.
>Doktor Tim wrote:
> Look elsewhere for your problem if the filter is in good order.
If the filter *is* clogged, replace it. Note the date and milage for future
reference.
>The fuel filter (Bosch) is designed to stop the passage of water. It will
clog before it gets >through, by design.
>I. The fuel filter's position, Horizontal, does seem to give water a
place to collect, acting >as it were to be a water separator. I'm not
aware though of any "media" that would plug at the >introduction of water.
The fibers I am aware of that will absorb water is a long list. These type
of fibers along with man-made fibers is designed to absorb and hold the
water. As the absorbtion load increases, the media swells. As the load
carrying capacity is approched, flow is reduced. Drain the old filter. Blow
through it. Compare effort to a new filter. You tell me, is flow
restricted? Empirical evidence is yours for the effort. Note evidence in
your paperpencil record.
>Gas and water do not mix.
>II. While my van is parked level, my drive way is 11 degrees inclined; so
when I back out the >horizontal filter with it's load of water gets
sloshed. If the filter has some water in it, >water may be introduced
into the fuel line pickup.
If one eye dropper of water actually went through the filter, there is less
than a 50/50 chance it would get through an injector nozzel without
clogging the nozzel for several seconds. Hook up an injector with a water
pump system pressure of 35 lbs. Activate the injector with 12v current.
Check the spray pattern. Piddling, isn't it. Water is a considerable higher
viscocity than gas. Set a bottle cap full of gas next to one of water in
open atmosphere. Note time. Note time interval of gas evaporation
completion. Note time interval of water evaporation completion. Divide
first by last. Note a very small number.
If you are using a non Bosch filter, you may well be passing water drops.
That could only happen with a Bosch filter if the matrix of the media was
split or bursted. All things, no matter how improbable, are possable.
Therefore, verify fuel pressure/filter first, without exhaustive
speculations. If you cut open the old filter (if it's a Bosch), then
squeeze the media over a pan, you will have empirical evidence of the truth
in the form of greater or lesser water in the pan.
If you then have confirmed a water problem not due to just an old filter
that has served a useful and completely reasonable life, or a non spec
filter, then address finding the anomaly that provides for excess
condesation in the tank, or question the sources of your fuel. Even the
best of Chevron stations might in a rare case pump you a pint of H20 along
with the 20 gallons of gas. If you confirm excess water in the tank is
present, drain it before subjecting a new filter to this abnormally
initial, life shortening, load.
Doktor Tim
Maintenance Repair and Restoration of European Vehicles
San Juan Island, WA