On the previous 80 Vanagon that I did this to, I added a SECOND inlet
side filter ahead of the Bosch one. It was a translucent white one and I
could tell when it was beginning to look reddish brown.  I found I could
just take the inlet side of of it loose and dump out most of the rust.
Like Angus's experience, after a couple of times, the interval went up
considerably. One other thing I did was blow some air back into the tank
which reduced the accumulation on intake screen.  Apparently there is a
hole in the screen that lets some of the rust come thru. After blowing
backwards on the hose, some of the rust ends up in the lower part of the
sump,
We'll see how the process works on the 91. (And the 87, sounds like its
time may be here too!)
Al Brase

Angus Gordon wrote:

>  The tank
> outlet is 11mm (about 7/16") as Al noted, and I couldn't find filters in
> this size so I forced a 3/8" fuel line on the outlet side of the tank and
> used a NAPA 3002 filter. This is a clear plastic filter so I can keep an
> eye on it's condition. I also changed the stock Bosch filter after the
> pump.
>
> Initially I had to change the inline filter after just a few hundred
> miles
> as the tank kept expelling it's load of rust, but the interval increased
> rapidly. Now, 4 years and 60,000 miles later the pump still works fine
> and
> I'm reminded by all the problems on the list, to check my fuel filter. It
> looks a little cloudy, and according to my records it has 12,000 miles on
> it, so I'll invest the $3.79 and put a new one on. Cheaper than a new
> tank.
>
>