Main Menu

How does the fuel sender work?

Started by Artful, February 22, 2011, 02:36:18 PM

Previous topic - Next topic
Print
Go Down Pages1
User actions

Artful

February 22, 2011, 02:36:18 PM
In the continuing saga of my Trailtech Vapor install I have finally hit a wall I can't beat my head through.

So four wires coming off the tank...

Two are grounds
(Brown/White) comes off the injector relay and powers the fuel pump.
(Blue/White) runs to the dash and I'm sure is the missing link in powering up my fuel light when the sender gets low.

Beyond that, stumped. I assumed that it worked like the oil pressure and neutral: Run power through the bulb, through the wire in the dash to the sender on the tank. When fuel gets low, switch grounds, light comes on. Wired it up that way and for one reason or another it isn't working.

I have too many house projects going to attack this in the next few days but if anyone can shed some light on how the sender works or how I should be testing with a multimeter, please enlighten me.

Any insight is greatly appreciated.
Every time I meet a new group of your friends that understand you and your weird sense of humor I'm a little more amazed that there are other people in the world like you that lived through childhood - My loving girlfriend

ducpainter

#1
February 22, 2011, 02:43:55 PM
My fuel sender doesn't work.  ;)

Not sure if you saw this...http://www.ducatimonsterforum.org/index.php?topic=46438.0

Maybe it will shed some light.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


Artful

#2
February 23, 2011, 07:13:20 AM
It may... and may explain why I was getting the readings I was.

The short version is (and I know you've been following along) that when I measured that circuit I wasn't getting any current even when fuel was low.

Testing procedure was as follows:

1. Pump out most of the gas in the tank.
2. Attach stock gauges.
3. Start bike.
4. Let bike run until factory gauges showed low fuel.
5. Disconnect stock gauges without turning off the bike and attach my harness.
6. Measure voltage between fuel sensor wire and 12V+

Seeing that thread and finding out that the sensor is in fact far more sophisticated than I expected (I figured it was simply a variable resistance being reported and that the electrical voodoo logic to illuminate the light was handled elsewhere) I can make the following assumptions.

1. The self-test lighting at start up has nothing to do with the fuel level, which I suspected from the beginning.
2. The factory light doesn't come on immediately because of the "analog filter" or check properties of the capacitor.
3. When I let the gas run out enough that the factory fuel light came on then (without turning off the bike) swapped in my harness, the fuel sensor lost voltage and restarted the signaling filtering process.
4. I didn't wait long enough with my harness attached and the bike powered for the sensor to determine fuel was in fact low and ground, lighting the bulb.

So my schematic might have been right after all, I just was making an incorrect assumption that the sensor was always sending SOMETHING that varied linearly with the fuel level.

Hopefully will have time to screw with it this weekend and see if I'm getting closer or still completely baffled.
Every time I meet a new group of your friends that understand you and your weird sense of humor I'm a little more amazed that there are other people in the world like you that lived through childhood - My loving girlfriend

Speeddog

#3
February 23, 2011, 08:31:08 AM
The fuel level sensor does take a bit of time to 'decide'.

I'm sure this is so that it's not flickering on and off like crazy as fuel sloshes around.

Send your thanks to Ducvet for this nugget of info.  [beer]
- - - - - Valley Desmo Service - - - - -
Reseda, CA
(951) 640-8908

~~~ "We've rearranged the deck chairs, refilled the champagne glasses, and the band sounds great. This is fine." - Alberto Puig ~~~

Artful

#4
February 23, 2011, 08:34:54 AM
If it turns out to be the magic bullet that finishes this project, I'll swing by on my next business trip and buy him a beer personally.
Every time I meet a new group of your friends that understand you and your weird sense of humor I'm a little more amazed that there are other people in the world like you that lived through childhood - My loving girlfriend

ducpainter

#5
February 23, 2011, 11:02:39 AM
Quote from: Speeddog on February 23, 2011, 08:31:08 AM
The fuel level sensor does take a bit of time to 'decide'.

I'm sure this is so that it's not flickering on and off like crazy as fuel sloshes around.

Send your thanks to Ducvet for this nugget of info.  [beer]
I just bring my bike to him.... ;)
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


Artful

#6
March 15, 2011, 06:29:25 AM
So the saga continues. When I run power through the bulb through the sender wire which then goes to ground, I have a constantly lit bulb. But when I measure resistance between the tank sender wires I am getting 4.1Kohms. Seems like that would be enough resistance to prevent the bulb from lighting eh?
Every time I meet a new group of your friends that understand you and your weird sense of humor I'm a little more amazed that there are other people in the world like you that lived through childhood - My loving girlfriend

errazor

#7
March 15, 2011, 09:22:03 AM
On My 07 s2r the fuel level sender isn't a switch but a thermistor.I believe it works like this: a steady current is run thru the thermistor, when the fuel level is above the thermistor the fuel cools it down. When the level is under the thermistor heats up and it change its resistance. You can't connect a bulb or a LED directly. the thermistor needs an amplifier circuit.
76 SUZUKI GT 100,  88 YAMAHA TDR 250,  07 DUCATI S2R 1000.

Artful

#8
March 15, 2011, 10:04:39 AM
Looks that way. I disassembled the cluster and it's a pretty complex circuit for fuel. Probably (definitely) beyond my knowledge level. So, scrapping the fuel light...
Every time I meet a new group of your friends that understand you and your weird sense of humor I'm a little more amazed that there are other people in the world like you that lived through childhood - My loving girlfriend

Staggerlee

#9
March 15, 2011, 10:55:25 AM
Quote from: Artful on March 15, 2011, 10:04:39 AM
Looks that way. I disassembled the cluster and it's a pretty complex circuit for fuel. Probably (definitely) beyond my knowledge level. So, scrapping the fuel light...
There may be something in this here thread that you might find helpful:

http://forum.svrider.com/showthread.php?t=44747&referrerid=27591

In a nutshell, this feller builds a harness that allows the fuel sender on his SV650 (also a thermistor type) to trip the fuel indicator on his Acewell gauge.  I'm helping a buddy fit a Koso gauge to his SV1k and we've got the harness put together but have yet to wire it in, so I have no idea yet how/if it works.

greenmonster

#10
March 18, 2011, 02:20:58 PM
Carbed info, maybe some help.

When I replaced the bulb w a LED,
I had to have a fat resistor on the signal wire, like for LED indicators.
Something like 54k, IIRC.
Lightened up at 13,5 L.
M900 -97 
MTS 1100s  -07
Print
Go Up Pages1
User actions