[Diy_efi] Sending unit confusion

Perry Harrington pedward at apsoft.com
Thu Feb 20 20:58:46 GMT 2003


I'd just hook a pot up to a 3.5v power supply, then attach a ruler or something
similar to the float arm, then cycle it up and down.

If the voltage fluctuation is 0-3.5v, then a pot that varies between 0 and 3.5v
would emulate the sending unit.

Barring that, you'd want to find out what the bias resistor is in the car, then
duplicate that on the test bench.

--Perry

On Thu, Feb 20, 2003 at 03:46:36PM -0500, Toyota Supra wrote:
> 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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-- 
Perry Harrington			Data Acquisition & Instrumentation, Inc	
perry at dainst dot com					 http://www.dainst.com/

Those who would give up essential liberty to purchase a little temporary safety
deserve neither liberty or safety. Nor, are they likely to end up with either.
                             -- Benjamin Franklin

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