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Date:         Fri, 19 Jan 2007 13:19:29 +0000
Reply-To:     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
Comments: To: RAlanen@AOL.COM
In-Reply-To:  <cc7.895c519.32e20767@aol.com>
Content-Type: text/plain; charset=us-ascii

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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