I just went through this issue with my 1985.  Certainly the first thing to
try is replacing the fuel filter, but if this doesn't solve the problem
there are other possible causes.  The noise is likely caused by cavitation
due to clogging prior to the pump.  The clog could be in the fuel tank,
fuel filter, fuel pump, or any combination of these.

If your 85 has the box filter before the pump, that is good; it should
prevent clogging in the pump.  VW went to the larger fuel filter in 1986
due to California smog regulations requiring a minimum filter replacement
schedule of 30,000 miles.  Unfortunately, there was not enough room between
the fuel tank and fuel pump for the larger filter, so it had to be
relocated after the pump, allowing grit in the fuel  to end up in the pump.
 If there is grit in the pump, tapping it on  your workbench may knock some
out.

There is a screen in the fuel tank outlet that can clog up.  Unfortunately,
there is no way to clean it.  The tank must be replaced.  If you replace
the tank, you should also replace the crossover tube and the fuel expansion
tank gravity vent valve grommets.  And of course if your 85 has the
original fuel lines, all of those should be replaced!

On Mon, Feb 13, 2012 at 12:16 AM, Graham Janson <graham.janson@gmail.com>wrote:

> Hi Mike
>
> Replacing the fuel filter will likely solve the problem.
>
> Standard message about "replacing all the fuel lines and the plastic
> nipple through the firewall while you're down there" applies.
>
> Graham
>
> On 2012-02-13, at 8:00 AM, Automatic digest processor wrote:
>
> > Subject: Re: Strange Engine Noise 85 Vanagon
> >
> > I'm just going to throw this out there--I had a noise almost like the
> > door-open-key-in-the-ignition/seat belt buzzer thing.  I realized after
> > moving the ol' ear around a litte that it was the fuel pump whining.  I
> > realize you said its "the engine" making the noise but I didn't know how
> > specific your diagnostics were to put it there so I thought I would throw
> > this out just in case.  It would make noise any time the engine is
> running
> > and would not change whether in gear or not, so it kinda fits.
> >
> > mike
>