[Diy_efi] Sending unit confusion

Fri Feb 21 03:50:16 GMT 2003

Hmm, don't electric motors generally hate stopping and starting? I'd be
leaving it on the whole time. I haven't really looked at your fuel
system wrt fuel flow, but I'd imagine your fuel reg will take care of
the high pressure side, and leaving your low pressure pump on all the
time is only going to fill your surge tank to capacity (which is what
you want) and then overflow back into the main tank.

I'd be worried about reliability issues (and the kiss principle) if one
was to start turning pumps on and off mid-flight so to speak.

PS: supra's rock hard!

Esteban :)

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
On Behalf Of Mark Bowers & Family
Sent: Friday, 21 February 2003 0:44
To: List for general do-it-yourself EFI talk
Subject: Re: [Diy_efi] Sending unit confusion

Hi J,

OK, I Have read you post on the voltages you are reading on the 'yaller'
wire. The reason that it reads 12 v when disconneted is that you are
measuring back into the open circuit that is normally the output of the
guage or internal dash regulator.

The key fact that you have measured is the 0 to 55k range of the pot. In
the best version of your application, the voltage feed will come from
the circuit, not the dash. Question: Does this auxiliary half of the
tank hook to a fuel guage? Will you leave this connected?

While starting to draw this up today, I had a new qyestion: Do you
really want this transfer pump running all the time? It will reduce the
pump's reliability by a lot. An alternative is to have the transfer pump
actuate in a cyclic basis to pump so much fuel at a time. Whether this
works or not depends on your use. If you are racing, espcially off-road
or some racing where the fuel can easily slosh back to the auxiliary
tank, it might better to run the transfer pump all the time, like you
seem to be planning.

Mark B.
----- Original Message -----
From: Toyota Supra <turbosupramk3 at hotmail.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, February 20, 2003 3:46 PM
Subject: Re: [Diy_efi] Sending unit confusion

> ok, just to be clear, this sounds like you want me to do this in place

> of the sending unit, is there a way to make the sending unit work 
> outside of the car, but putting 12vDC into the yellow wire, and then 
> putting
something
> on the other side of the second wire (brown with black)?
>
> the particular reason this appeals to me, is i can then move the float

> up and down, and watch it turn the circuit on, and turn it off, as 
> well as visually see how much travel the float has to make, before 
> overcoming the hysteresis.
>
> if not, i'll pick up a 55k pot today, the manual says that it should 
> read
0
> to 55k when functioning properly
>
> thanks perry
>
> -j
>
>
>
>
>
>
> >From: Perry Harrington <pedward at apsoft.com>
>
> >Subject: Re: [Diy_efi] Sending unit confusion
>
> >
> >Measure the highest resistance of the sending unit, then substitute a

> >pot of the same general value.  Just use 2 poles of the pot and leave

> >the 3rd
pole
> >unconnected.
> >
> >--Perry
> >
> >On Thu, Feb 20, 2003 at 03:12:35PM -0500, Toyota Supra wrote:
> > > that makes sense, so it measures the current loss, it is sending 
> > > 12vDC
> >out,
> > > but after grounding or whatever, only receives 0 to 3.5vDC ?
> > >
> > > so, how can i simulate what is in the car? can i measure 
> > > resistance
> >between
> > > the brown w/ black wire, and ground, and then use that resitor 
> > > between
> >my
> > > inverters ground and that particular wire? as well as running 
> > > 12vDC
into
> >the
> > > yellow wire?
> > >
> > > thanks for the help perry
> > >
> > > -j
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > >Subject: Re: [Diy_efi] Sending unit confusion
> > >
> > > >
> > > >The sending unit may be connected like a temp sensor.  The sender

> > > >has a bias resistor between ground and the input.  12v is 
> > > >supplied to the input of the sender and the output pulls the 
> > > >voltage up or down
through
> > > >the bias resistor.  If the sending unit isn't grounded, then with

> > > >2 wires it has to be biased externally.
> > > >
> > > >--Perry
> > > >
> > >
> > >
> > >
> > >
> > > > > >
> > > > > > > in my never ending quest to conquer this circuit, i have
> >encountered
> > > > > > > something very strange. when i removed the fuel level 
> > > > > > > sending
> >unit
> > > >to
> > > > > >try
> > > > > > > and test my circuit, i found that i am not able to 
> > > > > > > simulate
its
> > > > > >electrical
> > > > > > > function.
> > > > > > > the sending unit has 2 wires, a yellow and a brown w/ 
> > > > > > > black
> >tracer.
> > > >when
> > > > > >the
> > > > > > > sending unit is not plugged into the body harness, the 
> > > > > > > yellow
> >wire
> > > >has
> > > > > > > +12vDC (or whatever battery voltage may be) on the body
harness
> >side
> > > >of
> > > > > >the
> > > > > > > connector, and the brown w/ black tracer has approximately

> > > > > > > 15k
> >of
> > > > > >resistance
> > > > > > > to ground, or 35mV of positive voltage.
> > > > > > >
> > > > > > > when the connectors are plugged in, the yellow wire will 
> > > > > > > have
> > > >anywhere
> > > > > >from
> > > > > > > 0 to 3.5vDC, dependent on the position of the "float". the
> >variable
> > > > > >resistor
> > > > > > > will have resistance ranging from 0k to 55k.
> > > > > > >
> > > > > > > now, my problem is, i can't simulate the variable voltage
> >outside of
> > > >the
> > > > > > > vehicle, to test my circuit. if i put 12vDC into the 
> > > > > > > yellow
> >wire,
> > > >the
> > > > > >brown
> > > > > > > w/ black tracer will also have 12vDC, so what could that 
> > > > > > > wire
> > > >possibly
> > > > > >be
> > > > > > > doing, or connected to, that would make the circuit and 
> > > > > > > unit
> >work
> > > > > >properly?
> > > > > > >
> > > > > >
>
>
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