The larger filter catches much smaller particles. Small particles can erode the injectors changing the spray patterns or making them leakers. It also traps some water. The small filter before the pump has the disadvantage of being a restriction on the suction side of the pump increasing the chance of vaporizing the fuel before the pump and causing various running problems. Except for the in tank screens, most cars these days do not have filters on the pump inlets.

Dennis

----- Original Message -----
From: David Bohannan
Date: Tuesday, August 15, 2006 6:23 am
Subject: Re: Fuel filter
To: vanagon@GERRY.VANAGON.COM

> I like the idea of BOTH filters...but I tend to be a king of
> overkill...
> Maybe after VW looked at the fact that the fuel pump wouldn't be
> negativelyaffected by CRUD that would fit into a line going into
> the fuel pump...I am
> not agreeing with that...and then they decided that if one of
> the components
> of the fuel pump itself were to breakdown, they wouldn't want
> that to be
> forced into an injector....
>
> Just some senseless thought around why they did what they did...
>
> Maybe I will add the larger filter after the fuel pump on my
> 85's :-)
>
> Dave
> 85 GL "Baby Bus"
> 85 "Goldy"
>
> On 8/15/06, Jeff Oxroad wrote:
> >
> > I don't remember the year it all changed, but THE ONLY fuel
> filter on my
> > 83.5
> > Westy from the factory is that square plastic fuel filter.
> It's before the
> > fuel pump--that is to say between the gas tank and the fuel pump.
> >
> > That larger round metal canister fuel filter, as Dennis said, was
> > installed
> > after the fuel pump.
> >
> > Question I have is: don't we want a filter before the pump to
> keep crud
> > out
> > of the pump? And then, on the newer models is the canister
> filter AFTER
> > the
> > pump the only filter?
> >
> > Best,
> > Jeff
> > 83.5 Westy
> > LA,CA
> >
>
>
>
> --
> Dave - KC9FYM
> http://fjazzbass.blogspot.com
>