yes, I have opened both kinds.

both pleated paper element, the can filter bigger and more paper.

I put a pre filter on when i swapped in I4 gas for original diesel.
Good thing I did, for that summer, on long back road trip, the pre
filter blocked up with crud in what was once diesel tank. Had to
rinse it out with white gas, a couple of times, until I got back to
civilization and could get a new one.

I have pics of the can filter split open, did that when I replaced it
on my syncro.

see here:

http://shufti.wordpress.com/2010/08/03/syncro-fuel-filter-replacement/

alistair

On 6-Oct-10, at 3:04 PM, John Rodgers wrote:

  OK. Has anyone ever cut one of each of these filters open and looked
inside? I have not, so can't really address nor compare the issue of
filter type.material.

John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com

On 10/6/2010 4:26 PM, Old Volks Home wrote:
> The Square "Pre-Filter" is just that - a FILTER, not a strainer as
> you would
> be led to believe by that Digifant Book.  VW 133 133 511.  This was
> used as
> the ONLY filter on 75-79 Fuel Injection L-Jet engines on Beetles
> and Buses.
>
> In a difference of opinion with Scott, a Pre-Filter and the downstream
> Cannister Filter was used on 82-later Air 2.0&  Water Boxer 1.9
> engines
> through at least 85, particularly on the California Models.  I know
> because
> I have owned both in the past 18 years. Only an 80 2.0 I once owned
> just had
> the plastic Square Filter.  And I continue to run both on both my
> 84 GL and
> 84 Westy as they originally came with.
>
> VW did away with the Pre Filter on the Digifants because the Fuel
> Pumps of
> the era and replacements since then have a screen mesh inside the
> Fuel Pump
> Inlet.  Not really comfortable with the adequacy of that, so I
> would run a
> Pre Filter anyway if I had a choice.
>
> My nickel's worth and YMMV
> --
> Jim Thompson
> 84 GL 1.9 "Gloria"
> 84 Westfalia 2.1 "Ole Putt"
> 72 411 Station Wagon "Pug"
> 75 914 1.8 "Nancy"
> Full Timing Since March 1999
> oldvolkshome@gmail.com
> http://www.oldvolkshome.com
> ***********************************
> On Wed, Oct 6, 2010 at 1:26 PM, John Rodgers<inua@charter.net>  wrote:
>
>>   In working with my two vans that were stored for 10 years, I
>> have had
>> to deal with many issues. One was getting the fuel delivery system
>> working again. This included opening it up, and flushing all the old
>> fuel and junk from it. The injectors were frozen and would not
>> work, so
>> had to send them out for servicing. They work fine now. And the fuel
>> pump on my Carat was seized so that had to be dealt with. By removing
>> the pump, and spraying carburetor cleaner into it and allowing it
>> to sit
>> over night, then repeating the process, the pump freed up and now
>> works
>> just fine.Then there was the issue of the fuel filters.
>>
>> In as much as I'm having idling problems, I got out the Digifant Fuel
>> Injection System manual to study. I found interesting remarks
>> concerning
>> the fuel filters. In as much as there has been a good bit of talk on
>> this list about the large filter after the pump, and the small
>> filter in
>> front of the pump - here is what the book has to say about them.
>>
>> ************************
>>
>> *Fuel Filters*
>>
>> Two types of filters are used on the Digifant system.
>>
>> One is a square _*plastic fuel  strainer*_ which is mounted before
>> the
>> fuel pump *_to __protect the pump_* from foreign particles.
>>
>> The *_main fuel filter_* is a metal cylinder which mounts behind the
>> fuel pump. *_It has a finer filtering mesh to protect the fuel
>> injection
>> components._*
>>
>> Both are lifetime filters and do not require replacement under normal
>> circumstances.
>>
>> *********************
>>
>> Of interest to me is the different function of the two filters - the
>> first to protect the pump. the second to protect the FI
>> components, ie,
>> the injectors.
>>
>> I note that one is  a fuel STRAINER, while the other is a fuel
>> FILTER.
>> Quite a different between a strainer and a filter.
>>
>> I have read that the square strainer  can be left out, but after
>> reading
>> this - I would not. Each filter/strainer serves a different and
>> distinct
>> purpose and therefore both need to be in the fuel system..
>>
>> Just my $0.02.
>>
>> John
>>
>> --
>> John Rodgers
>> Clayartist and Moldmaker
>> 88'GL VW Bus Driver
>> Chelsea, AL
>> Http://www.moldhaus.com<http://www.moldhaus.com/>
>>
>