You could run it down by driving until you think it's near empty, and then
park it, shut it off, disconnect your battery (!), and drain fuel from the
tank (via siphon or better yet off the tank outlet) into however many
measurable fuel jugs it takes to measure what's really left. Requires little
to no disassembly and you'll have a true answer. Also not a bad time to
evaluate the state of your fuel lines from tank to pump and filter.

Good luck,
-Peter

On Tue, May 4, 2010 at 12:08 PM, Annie <lsandrsn@gmail.com> wrote:

> >
> > On Tue, May 4, 2010 at 9:51 AM, David Beierl <dbeierl@attglobal.net>
> >  wrote:
>
> I wonder if your uncle didn't try to lift the vehicle by the fuel tank (it
> > happens, the tank's in an unconventional location) and squashed it.  Easy
> to
> > tell, crawl underneath and look.
>
>
> David - It seems fine. The first gas fill-up was before he finished the
> other work and same thing. The other 2 tanks were last Thursday and Sunday,
> after the work was finished. So, I don't think it's a case of the tank
> getting squashed.
>
> Rob wrote:
> When I got it my '84 would not take/use over 12 gallons (3/4 tank), I
> changed the tank and that fixed the problem
>
> Rob - no idea why that happened or why? That does seem weird.
>
> On Tue, May 4, 2010 at 11:25 AM, Geo <ahwahneevw@gmail.com> wrote:
> >
> > How do you know the tank is empty or near empty?  i.e. I wouldn't assume
> > that a gas gauge in the red is accurate.  Several things, both mechanical
> > and electrical, can affect that gauge.
> >
>
> Geo - I have other indication. The needle movement from full to empty seems
> consistent but really, I have no idea. Is there any way I can tell for
> sure?
> Short of actually running it out of gas, which I'd rather not do.
>
> By my calculations for a standard Vanagon gas tank of 15.9 gallons, at
> about
> 21 mpg, I should be getting about 315 miles per tank. Does that sound
> correct?
>
> Thanks,
> ~Annie
>