Date: Mon, 29 Sep 2003 12:20:48 -0700
Reply-To: Harald Rust <harald_nancy_vw@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Harald Rust <harald_nancy_vw@YAHOO.COM>
Subject: Re: The "Other" Vanagon Syndrome, Part II
Content-Type: text/plain; charset=us-ascii
Someone was asking about the fuel tank strainer.
Taking off the fuel filter made it apparent that
there was no restriction in the fuel tank or
enroute to the fuel pump.
About the enigmatic Afm:
Many folks seem to think the bucking was caused
by the Afm. Symptoms were the same.
I agree with that, and during the trip, when
the bucking started, I was kicking myself for
not having taken the spare afm along.
Logic was if the afm goes bad, I could always
open the plastic cover, move over the resistor
board, clean it up with denatured alcohol and q-tip,
close it up with silicone or duct tape, and it
should get one back home.
I've worked on afms at home, and take my word for
it, I know when they're bad.
Here's a picture of my afm with the cap fix:
http://www.geocities.com/harald_nancy/intermitt._syndrome.htm
Afm is a pretty primitive piece of equipment, and
not much mystery there.
Hooking up the digitool, as I mentioned, shows
you instantly if the afm is working properly.
On the lcd volt meter on the digitool, you can observe
the voltage signal that the afm sends to the ecu
as you drive.
Comparing those numbers with notes and numbers
from other known working afms shows you whether the
afm is ok or defective.
There should be no wild fluctuations, and the voltage
signal changes gradually, as the engine sucks in more
or less air.
Anyway in a nutshell, the afm checked out fine.
Also that afm only has about 45,000 miles on it.
It still boils down to the fact that every time
I would add detergent to the fuel tank, the
vanagon would run significantly better.
Finally adding a heavy dose of Techron made
the bucking totally disappear after some driving.
It could be a coincidence, of course, but it
happened several times, and the pattern became
evident.
At home, we always get cheapest Safeway gas, and
I don't know if it has any injector cleaners in it.
I doubt it, and maybe finally the injectors clogged
up.
Some people say their vanagons run better on premium
gas. The waterboxer, being low compression, doesn't
need premium, but it probably does like the detergent
additives in premium gas.
Maybe that's the reason some vanagons run better on
premium and certain brands of gas.
Researching the various designs of fuel injectors
indicates that vanagons have the old-type needle
fuel injectors, which are prone to sticking,
either closed or open.
Newer cars use a different design, which are less
likely to clog up.
Harald
'90 westfalia
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