Put the pump down low.
This will not matter to you until the first time you
run the tank dry late at night in the rain, walk 5
miles to get gas in a 1 gal can, and then cannot get
started because the *fuel* pump is not a very good
*air* pump, and so will not prime.
(Ask me how I know)
Carter Shore
--- "Donald H. Locker" <dhl@chelseamsl.com> wrote:
>
> Fellow Spitsters,
>
> Not to be too contrary, but even though the initial
> loading (priming)
> of the fuel pump will be with suction, after the
> pipe is full from the
> bottom of the tank to the pump, there will no longer
> be any gravity
> for the pump to overcome -- the rising fuel is
> exactly balanced by the
> falling fuel, and as long as the pump is lower than
> the in-tank
> opening of the pick-up, this [siphon] action will
> reduce the lift
> requirement of the pump. Now the other side of this
> story is that the
> level of the outlet of the pump also affects the
> pressure differential
> that the pump operates against, and since the pickup
> point and the
> delivery are at a constant differential height,
> (depending on road
> grade, though) the pump operates against a constant
> head. So it
> doesn't really matter to the pump, (who probably
> doesn't even see this
> simple situation -- remember the carb float valve is
> closed most of
> the time, so the output is deadheaded. And as long
> as the pump is in
> the trunk, the fuel should be cool enough to stay
> away from vapour
> lock, so the fact that there may be suction on the
> supply side of the
> pump is nearly irrelevent. But wait! there's more!
>
> (Sorry to be so long-winded.) For safety, if you
> power the fuel pump
> through a relay controlled by lube pressure, you
> should be safer in
> case of serious shunt. And this would not
> significantly alter
> starting characteristics -- either there is
> sufficient fuel in the
> carb bowls to start, (in which case oil pressure
> rises quickly, pump
> begins delivering fuel, and all is ducky) or the
> cranking raises the
> oil pressure (albeit with a bit of delay) and the
> pump begins
> delivering, the bowls fill, engine starts, and
> THEY'RE OFF!
>
> Donald.
> (who saved up three weeks of postings just for this
> occasion!)
>
> > Date: Tue, 07 Mar 2000 09:01:34 -0700
> > From: Joe Curry <spitlist@gte.net>
> >
> > "Terry L. Thompson" wrote:
> > >
> > > I've been debating where to mount my electric
> fuel pump,
> > > and one of the suggestions is that the pump
> should be below
> > > the fuel tank (when the car is level) so that
> the pump is
> > > gravity fed, and has less work to do.
> >
> > That is not so with the later Spitfire tanks. The
> reason is because
> > regardless of where the pump is located, the fuel
> is sucked out of the
> > tank from above via a suction tube that is located
> on top to the right
> > of the fuel inlet. On earlier bottom feed tanks
> it does apply.
> > >
> > > The two places I've considered are A) in the
> trunk near
> > > the gas tank which is some distance from the
> carb or B)on
> > > the frame perhaps next to the starter, which
> puts it very
> > > close to road debris from the tires.
> > >
> >
> > Because of safety concerns, I located mine in the
> trunk. Shoiuld one of
> > the rubber hoses rupture the fuel would be kept in
> the trunk area rather
> > in the engine compartment next to heat and sparks
> (starter commutator).
> >
> > > If anyone has a decent mounting point, away from
> a hot spot
> > > and interference of moving parts, I'd like to
> know, so I
> > > only have to re-run the fuel line once.
> > >
> > Mine is to the left and below the tank in the void
> between the tank and
> > the floor of the trunk.
> >
> > Regards,
> > Joe
> >
> >
> > --
> > "If you can't excel with talent, triumph with
> effort."
> > -- Dave Weinbaum in National Enquirer
> >
>
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