The original set-up you had probably included the pre-pump filter
(factory-installed to catch new-tank debris, then dealer-removed at a later
service) and the after-pump main filter.
  The pump can pass small particles with no problem, to be caught by the
main filter before it goes to the injectors.  Any pre-pump restrictions
(tank screen, small inlet diameter, clogged pre-filter, etc can cause pump
cavitation, which can be quite noisy.
  Some folks replace a noisy pump, only to find that the new pump is just as
noisy, due to a restriction ahead of it.  Sometimes the tank must be changed
to fix the noise.

Mike B.

--------------------------------------------------
From: "Scott Chapman" <scott_list@MISCHKO.COM>
Sent: Tuesday, May 11, 2010 2:22 PM
To: <vanagon@GERRY.VANAGON.COM>
Subject:      Re: Vanagon Gas Tank/Fuel System measurements

> Why does the filter go after the pump?
> On my '85, the white plastic filter was between the tank and pump.  I
> put the new big metal one there.
> There is no filter after the pump on my rig.
>
> Is this Ok or am I missing something?
>
> craig cowan wrote:
>> Problem solved (I believe).
>> I just spoke with Ken who cleared up that my new tank has the larger
>> output
>> so i can run 11mm hose from the tank to the pump, 7mm hose from the pump
>> to
>> the filter, and 7mm hose thereafter. Essentially going with the '86+
>> designed fuel system.
>>
>> Thanks again everyone!
>>
>> -Craig Cowan
>>
>>
>> On Tue, May 11, 2010 at 11:29 AM, craig cowan <phishman068@gmail.com>
>> wrote:
>>
>>
>>> So I have this '85 bus which has been plagued with gas tank problems.
>>> I have a brand new tank from Ken Willford at Vanagain that's going in
>>> today. It has an 11mm outlet, which i believe is the same size as the
>>> stock
>>> one (But can't get under the bus at this time to check).
>>> As I recall, the inlet to the fuel pump is also 11mm. Right? Then the
>>> outlet to the fuel pump is smaller..... 7mm?
>>>
>>> I know the current system I have is very gerry-rigged with it's fuel
>>> filter
>>> and I plan to do it right this time. So..... the large metal filters
>>> which
>>> normally go after the fuel pump, are 7mm on both sides? Or do I have
>>> this
>>> mistaken?
>>>
>>> I planned not to use the plastic prefilter if I can avoid it, but if i
>>> need
>>> to pick one up as an adaptor i need to know ASAP.
>>>
>>> -Craig
>>> '85GL turned WESTY
>>> BOSTIG in the back
>>>
>>>
>>>
>>
>>
>>