Re: [DML] fuel sending units

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

On 10/05/2012 19:01, Stephen Rice wrote:
> I honestly like the idea of the valve on the baffle of the new Houston
> fuel pump.  It does sound like a good idea but honestly my tuna can is
> working fine.  You should never attempt to run a car bone dry.  You
> are just asking for problems with your fuel pump if you make it a
> habit to do this regularly.  Fuel pumps are designed to pump fuel, not
> air.
Agreed, but with a decent baffle setup, you have the ability to keep 
that fuel pumping nothing but fuel down to the last litre of the stuff. 
I know you carb guys are lucky and basically have a buffer tank.

Impeller-based lift pumps will cheerfully run in air BTW

The Houston sender light starts flashing when there's still nearly 20 
litres of fuel in the tank.


> What amazes me is the reaction towards the new fuel pump assembly.
> I've heard all sorts of criticism towards the tuna can and Hervey's
> baffle yet DMCH is basically doing the same thing now, except their
> new baffle has a valve instead of holes drilled in it.  The valve
> isn't going to magically pull fuel from the back of the tank.
You miss the point - fuel can get *in* the baffle but it can't *leave*. 
The engine actually only uses a very small proportion of the volume the 
pump needs to pump in order to maintain pressure. It dumps around 90-99% 
of the flow straight back into the baffle, so the rest of the fuel in 
the tank can be sloshed away from the baffle for minutes before the pump 
will be starved. Without that check valve, the pump only has fuel for 
the time it takes the baffle to drain out the small holes - maybe 15-20 
secs..

It'd be even better in the middle of the tank, but that check valve will 
make more of a difference alone.

Martin


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