[Diy_efi] Re: Looking for circuit to turn transfer pump off at certain voltages-another suggestion

John Petersen john at underwoodgroup.com
Thu Nov 14 20:21:54 GMT 2002


The solution provided at the bottom, having a tube between the two
lowest points in the tank, should work nicely. My recommendation would
be to have an upside down U shaped tube between the two tanks. At the
top of the U have a valve with a floating ball, which will open to the
tank when full, and close when there is no fluid above that level. This
will avoid having the siphon load up with air (it will be purged every
tank filling). 

This would take up very little more space than having a hose run across
the two for the proposed pump, and would require no electrics.

Hope this helps
-John

-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On
Behalf Of Thomas L. Frobase
Sent: Monday, November 11, 2002 9:20 PM
To: diy_efi at diy-efi.org
Subject: RE: [Diy_efi] Re: Looking for circuit to turn transfer pump off
at certain voltages

Well this is how I would approach the problem, Motorola now makes a 8
pin microcontroller that uses the same instruction set as the Megasquirt
project http://www.bgsoflex.com/megasquirt.html it has several Analog to
digital converters as well as status outputs, using the processor you
will be able to monitor the analog level of the tank and turn on and off
the pump as appropriate, it should require a handful of components and a
relay driver for the pump.  The controller uses pretty much the same
tool set as the megasquirt as well as having an internal oscillator as
not to require a crystal.  Sure, I know it will take a bit to program
the chip but in the end it will be simple reliable and inexpensive, the
single price for the chip MC69hc908QT4 is about $4.00.

... tom

-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On
Behalf Of Bevan Weiss
Sent: Sunday, November 10, 2002 11:32 PM
To: diy_efi at diy-efi.org
Subject: Re: [Diy_efi] Re: Looking for circuit to turn transfer pump off
at certain voltages



----- Original Message -----
From: "Toyota Supra" <turbosupramk3 at hotmail.com>
To: <diy_efi at diy-efi.org>
Sent: Sunday, November 10, 2002 4:02 PM
Subject: Re: [Diy_efi] Re: Looking for circuit to turn transfer pump off
at certain voltages


> hey bevan, thanks for the reply, maybe this will help clarify ...
>
>
> here are the specifics, my gas tank is a saddle tank, meaning that it 
> has two sides to it like saddle bags on a horse. now the pumps are on 
> the left side, and the mechanical venturi valve that used to transfer 
> the fuel from the right side, had to be removed.
>
> so my dilema is, how do i get fuel from the right side of the tank, to

> the left side where the fuel pumps sit, so that i am not driving 
> around on
only
> a 1/2 tank of usable gas, even though the entire tank is full?
>
> well, my design thought was to have a transfer pump intank, that drew 
> from the right side, to the left side, at all times that the car was 
> on, except for when the right side of the tank got low on fuel. this 
> is because the fuel acts as a lubricant to the transfer pump, and if 
> it ran dry for any period, it would probably burn up.
>
> so the way i decided to control the transfer pump was to use the 
> existing sending unit that is in the right side of the tank (which 
> reads 0 to 3.5v, full being 0v - bone dry being 3.5V) and use that 
> sending units output as
a
> reference signal for the circuit, and having that circuit turn a relay

> off (or on) to control the power to the transfer pump.
>
> i appologize if this reads confusing and that it is so long, but i 
> wanted
to
> be as detailed as possible. if you think your circuit design would 
> work,
i'd
> be very grateful if i could have a copy of it. thank you for the reply

Hmm, so you can't just have a tube connecting the two saddle-tanks
together at their lowest point (to distribute the fuel evenly over both
tanks), this would certainly be the easiest way to let the pump see two
tanks.  I realise that having the tanks connected in a more vertical
manner would be a better solution but it may not be worth the trouble.

I can't think of an optimum way of doing this (easily), as even a
comparator type circuit isn't what you really want, it would mean that
the pump is on when the tank is near full and off when the tank is
getting empty, which isn't an optimum idea, you wouldn't be able to use
all the fuel this way....

I think perhaps that looking outside the usage of a pump is required...
(or perhaps a non standard type of usage).

I have no real ideas about this kind of stuff, only the electronics and
that's not the ideal solution to this one.

FWIW, the comparator circuit that I was refering to was a simple opamp
(ie 741), with a VREF on the non-inverting input that is the switching
point of your fuel tank, and have the inverting input connected to the
actual fuel sensor itself (after sufficient low pass filtering).  Then
you can add in some hysteresis if required/desired simply by applying
some feedback to the circuit ( a resistor/voltage divider from the
output back to the non-inverting input).

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org http://www.diy-efi.org/mailman/listinfo/diy_efi


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi



More information about the Diy_efi mailing list