My '67 chevy hot rod camper has two tanks.  They are more-or-less
independent of each other.  I have two fuel pumps and a valve that
switches the line to the FI from one tank to the other.  I flip the
switch on the dash and it turns off one fuel pump, turns on the other
and sets the valve to allow gas from the correct tank.  I also have a
fuel gauge that has a toggle switch that can point to either tank.
Works great.

r

On Jan 10, 2010, at 4:09 PM, David Marshall wrote:

> <style type="text/css">
>        -></style>Volks,
> Today I am CADing up the auxiliary fuel tank idea
> so I can get quotes for the materials.
>
> The mailing that I sent
> out earlier asking for who wants what came in overwhelmingly that
> almost
> nobody wanted a tank that would have the ability to heat the fuel...
> so... done.  No longer an option.
>
> A few people said that
> they wanted two tanks &ndash; so a multisided fit was in order, so
> that
> makes the tank slightly smaller than my original design.  The square
> tank design that I have now is simpler to cut materials for and to
> manufacture, so it will cost less in the end which is a good thing.
>
> The tank design that I have as of now is 60.7L (16 gallons)
> capacity, so for the Diesel people at 10L per 100km would give an
> additional 600km of range.  Gasoline vans do about 14L per 100km so
> about 420km additional range, for people south of the border that's
> 370
> and 260 miles respectively.  No so bad I guess &ndash; I could drive
> my TriStar from Quesnel BC to Seattle WA on one fill up.  The tank
> will stick down 10cm / 4&rdquo; down from the lower section of the
> frame.  That makes the Syncro's drive shaft protection still the
> lowest point by approximately 3cm / 1&rdquo;
>
> Most people also
> said that they wanted to do a transfer pump system.  So, now I am at
> a loss to the absolute best way of doing that.  What transfers into
> what?  How do you fill the auxiliary tank in a reasonable amount of
> time?
>
> The only decent way I can see it to keep it simple and
> to keep the costs down is to have a fuel tank valve and a high flow,
> low
> pressure fuel pump and set it up the same way Herman did on his
> excellent
> Syncro project.  Here is the direct link to his diagram -
> http://picasaweb.google.com/itzdshtz/VanagonSyncroProject02#5346690182551978322
> - His diagram shows a two aux tank setup but would work equally well
> with
> one.  My only concern with the two auxiliary tank setup like his is
> once they are down to their last little bit of fuel, the chances of
> both
> running out of fuel at the exact same time will be quite low.  So
> with an engine sucking on a pipe that has a Y into two tanks, one
> side of
> the Y may have air when the other side still has fuel and then air
> will
> get into the system &ndash; not so good for a Diesel engine.  I
> think the solution to the two aux tank system would be to look at it
> like
> the auxiliary tank the fuel pump transfers the fuel into is the only
> tank
> that the engine draws from when you are in auxiliary tank mode.  The
> other tank can be looked at is if it was an &ldquo;auxiliary
> auxiliary&rdquo; tank and should be setup to gravity feed the main
> auxiliary tank.  This is less than an elegant solution and reminds
> me too much of my BMW R1100 GS tank &ndash; 25L in size, but you can
> only
> use 22L as the remaining 3L are always stuck on the other tank lobe...
> and a whole different discussion on another mailing list!
>
> The
> other issue I have with the transfer pump idea is fulling the
> auxiliary
> tank(s).  A Vanagon electric fuel pump does about 2L a minute?
> So it will take 30 minutes to transfer the fuel from one tank to the
> other... that's not fast enough &ndash; I want to be able to fill both
> tanks at the filling station at the same time!  The issue with
> pushing fuel faster than this is because the Vanagon tank is 70L and
> the
> aux tank is 60L there is a chance of FILLING the aux tank to 100%,
> so you
> would have to be a line going back to the main tank to act as an
> overflow
> &ndash; to keep that safe, it would have to be able to exceed the flow
> rate of the pump pushing the fuel into the auxiliary tank and we're
> limited to the flow rate of 8mm fuel line or put this line into the
> main
> tank vent that goes into the fuel filler neck.
>
> In order to use
> both tanks as a supply to the engine, it would make sense to install a
> fuel level sender in the aux tank and connect it to a fuel gauge of
> some
> sort.
>
> So, please, I would like to hear some ideas about fuel
> transfer pumps and peoples experiences with them.  If we're going to
> build some aux tanks, I wanna to do right the first time!
>
> David Marshall
> VW Adventure Driver and BMW Adventure Rider
>
>
> HasenWerk
> http://www.hasenwerk.ca

I remain, as always
YrLyl&ObdntSrvnt,

r