Date: Fri, 19 Jan 2007 19:44:31 -0500
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: fuel pump fuel filter-stupid engineering
In-Reply-To: <064601c73c21$82dc6e20$657ba8c0@MAIN>
Content-type: text/plain; charset=us-ascii
As I was writing this I was thinking to myself, "Why don't I copy and paste"
it from the last go around? Somehow I think it was like 4-6 weeks ago, not
months. I sort of responded to the "Stupid" idea and tried to introduce some
reasoning behind the method. Would put the oil filter on the suction side of
the oil pump? May work most of the time but can you imagine priming at each
oil change? How sucking that cold thick oil through the filter? Gasoline
doesn't have the viscosity issue but vaporization can be. Oh, and if you get
enough vapor and some air into the pump, the arching on the brushes will
finish the pump off.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Robert Fisher
Sent: Friday, January 19, 2007 6:28 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: fuel pump fuel filter-stupid engineering
So I'm wondering, Dennis- do you actually sit down and re-write this thing
from memory every 4 to 6 months when this comes up again, or do you just
cut/paste and edit an old one? : )
I've only been on the list for 3.5 yrs thereabouts but sometimes I feel like
I can predict which posts will show up the next day, and from whom- makes me
wonder what it's like for the list immortals.
I'm actually not being critical, it's the way it has to be if the list is
to expand and the remaining Vanagons are to survive, but it does sort of
point out why threads about age and pleas for sympathy are not nipped short
but are actually welcome by many.
I used to read all the posts but since I don't have a Westy or a Syncro the
(endless) posts about refrigerators and likewise those about the Syncro
differentials and such go straight into the black hole these days... I
suppose everybody has some topics/posts that they don't even bother with
(and don't anybody say 'especially yours', very funny har har). : )
Cya,
Robert
----- Original Message -----
From: "Dennis Haynes" <dhaynes@OPTONLINE.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, January 19, 2007 5:19 AM
Subject: Re: fuel pump fuel filter-stupid engineering
Fuel systems for years had the filter between the pump and the carberator.
Of course diaphragm pumps only had to be protected from the bug stuff that
could jam a valve or actually bloc a line. That was usually done by a sock
or screen in the tank. Carberated engines also did not need to flow that
much fuel.
As we stepped into fuel injection, the pumps have more critical tolerances
and needed more protection. Some European cars would have the filters before
the pump. All the CIS cars and most American and Aisian cars have the filter
after the pump. Todays fuels are basically clean and the fuel injection
systems move fuel at a very high rates. Filters had to become finer to trap
smaller particles to protect the injectors, both for clogging and erroision.
That is why the big metal can. The big can is also considered a life time
filter, (ha). It is more effective to filter under pressure so that as the
filter fills, the efficiency will go up. If the filter on the suction side
gets any restriction at all the fuel will be under a vacuum and will quickly
vaporize. This will cause the pump to vapor lock and cavitate interfering
with fuel flow. The problem can become even worse during extended drives
and/or hot weather as the recirculating will pick up engine heat and
actually warm up the tank. Get the fuel to 120 degrees, put in under a
vacuum, and you got another cause of vanagon syndrome.
Unless you have a rusty tank or fill from gas cans or other dubious sources,
there really is no need for the pre filter. Small stuff will pass through.
Remember there is also a screen in the pump inlet. The after pump filter
will clean the fuel and do to the recirculation, the tank fuel will become
well filtered. The 86 and later 2wd did come with the pre filter which was
supposed to be removed at the first service. Maybe they were worried about
debris from the new tank. My experience so far though is that when the pumps
have premature problems, it is usually due to a bad tank. I only use the
pre-filter when an adapter is needed to connect the after market tanks to
the pump.
Dennis
----- Original Message -----
From: Frank Condelli
Date: Friday, January 19, 2007 6:42 am
Subject: Re: fuel pump fuel filter-stupid engineering
To: vanagon@GERRY.VANAGON.COM
> In a message dated 19/01/2007 12:11:31 A.M. Eastern Standard Time,
> LISTSERV@GERRY.VANAGON.COM writes:
>
> I thought the same damn thing. Why on earth would the filter be
> after the
> pump? It wasn't like this pre-86' I think. At least it wasn't on
> my 85'.
> The filter was the litttle square plastic one and was before the
> pump.
>
> I have heard of people filtering before and after on their
> Vanagon. Does
> anyone know if there is any real benefit or detriment to this?
> I mean common
> sense says two filters are better than one - but you just never
> know what
> that could do.
>
>
>
>
>
> This subject was discussed in GREAT detail by many a few months
> ago. Check
> the archives for a winters night reading on the subject.
>
> Cheers,
>
> Frank Condelli
> Almonte, Ontario, Canada
> '87 Westy, '90 Carat, '87 Wolfsburg (Forsale) & Lionel Trains
> (_Collectionfor sale_
> (http://members.aol.com/Fkc43/trainsal.htm) )
> Vanagon/Vanagon Westfalia Service in the Ottawa Valley
> _Frank Condelli & Associates_
> (http://members.aol.com/Fkc43/busindex.html)_Vanagon Stainless
> Steel Exhaust Systems_
> (http://members.aol.com/Fkc43/stebro.htm)
> _BusFusion_ (http://members.aol.com/BusFusion/bfhome.htm) a VW Camper
> camping event, Almonte, ON, June 07 ~ 10, 2007
>
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