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? about fuel sensor resistance ???

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  • #1

    ? about fuel sensor resistance ???

    I've installed the Acewell 2853 gauge on my 79XS11SF. Trying to troubleshoot why the fuel light is not reading proper fuel level. I'm reading that I first need to know the resistance range of the sender,...I guess there is an ohm reading for when the fuel is full and empty. Once I know this, there is a setting on the gauge.

    I'm not good with this stuff,..hopefully I am asking the question the right way. Please explain for dummies
    Rob - 79 SF
    Tags: None
  • #2
    First off, you have a Special. They do NOT use a fuel gauge, but a low fuel warning light. I have NOT looked at one, but if it does not go in a line, from say 370 Ohms to 130 Ohms as the fuel level drops, it will not work. I THINK, and again, I have NOT looked at the Special that close, the sender is more of an off/on switch. The Standard has a fuel gauge, and it DOES "flow" from one resistance to another. The only thing is, it mounts on the other side of the tank, so it would read backwards, starting empty and going to full on the stock gauge.
    I know, not much but I'm at work, so I do not have the Yamaha manual handy and as I'm getting older, CRS kicks in earlier...
    Ray Matteis
    KE6NHG
    XS1100 E '78 (winter project)
    XS1100 SF Bob Jones worked on it!

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    • #3
      The SF sending unit does not have a range (Full - Empty) it just comes on when your fuel level gets low (indicator light). Unless you have swapped in a standard tank. If that is the case pull the sending unit and use a multimeter to see what resistance is is at full and empty.

      Not sure if I explained that well enough or not.

      DiverRay typed faster than me...
      Ty

      78 XS1100E - Now in Minnesota
      80 XS1100LG - The Punisher
      82 XJ1100 - Current project - The Twins
      82 XJ1100 - Wife's Bike - The Twins
      82 XJ1100 - Daughter's Bike
      72 Suzuki TS125 - Daughter's Bike
      72 Yamaha Mini JT2 - Youngest Daughter's bike (She wants a bigger one now)

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      • #4
        Thanks guys. I have not swapped to a standard tank.

        I'm pretty sure the new digital gauge I have reads the fuel level by the amount of ohm resistance when full or empty. Is there an ohm range for this bike? I need those #'s so I can tell the gauge so it communicates properly. Was hoping there was a standard answer as I don't have a multi-meter nor would I know what to do with it if I did.

        My last resort would be to bring to a mechanic to measure, but hoping to avoid that.
        Rob - 79 SF

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        • #5
          As I'm re-reading your answers, I'm not sure if I'm asking my question properly. Is there a way for my bike to tell the Acewell what level of fuel I have in the tank?

          Or is the answer simply "no" and it will just tell the Acewell when I have low fuel,..if even that?
          Rob - 79 SF

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          • #6
            The answer is NO. The Special does NOT have a fuel sending unit, but a low fuel light. You will need to find a Standard fuel sending unit to use the gauge. Check with andreas, he may have a spare.
            Ray Matteis
            KE6NHG
            XS1100 E '78 (winter project)
            XS1100 SF Bob Jones worked on it!

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            • #7
              Thanks Diver. Sounds complicated. Is this a major modification? I just Googled but I have not idea what I'm looking at...
              Rob - 79 SF

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              • #8
                TC has a great thread regarding his digital dash and his quest for fuel metering. Brian on the XS Aussie site, along with the UK site has a few write-ups regarding his Acewell gauge. Thing is, these gauges are meant more-so for modern bikes. You have to have a more-extensive electrical background to install them. Definitely not for the faint-hearted.
                1979 XS1100F
                2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.

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                • #9
                  Flaming Death Warning

                  Originally posted by mrhammer2u View Post
                  ... I just Googled but I have not idea what I'm looking at...
                  Dear Mr Hammer 2U,

                  PLEASE! do not tamper with the fuel tank and the low fuel warning light system to add a fuel gauge to your XS1100 Special!

                  All of the XS1100 Special models use a 12v thermistor in the fuel tank to control the Fuel warning light. The voltage and current supplied to the thermistor -- and the tank itself along with the fuel inside the tank -- are not limited in any way, shape or form except by the thermistor. There is no linear change in resistance from 'Full' to 'Empty' that you need for a useful fuel gauge because it only starts to work when there's somewhere around a gallon of fuel left in the tank.

                  The thermistor itself is inside the fuel tank where it's normally covered and cooled by the fuel. The resistance is high when it's cool and the warning light stays off. As the fuel level in the tank drops it eventually uncovers the thermistor and the thermistor heats up. The resistance goes low until there's enough current for for the warning light to turn on.


                  The XS1100 Standard models all have a real fuel gauge but they also use a 12v to 7v stepdown voltage/current limiting regulator in the tachometer housing along with the actual gauge itself. There is a float and a variable resistor in the fuel tank that ranges from:
                  Full ~ 6 to 10 Ohms
                  Half ~ 28.5 to 36.5 Ohms
                  Empty ~ 75 to 85 Ohms

                  Again, the voltage and current supplied to the variable resistor for the fuel gauge and the fuel tank is limited by the 12v to 7v stepdown regulator in the tachometer housing.

                  Please do not try to use the unregulated 12v supplied by your XS1100 Special to run any type of Yamaha factory or aftermarket fuel gauge unless it is explicitly designed to use 12v.

                  Have a flaming-death-free day!

                  .
                  -- Scott
                  _____
                  ♬
                  2004 ST1300A: No name... yet
                  1982 XJ1100J: "Baby" SS Brakes, '850 FD, ACCT
                  1980 XS1100G: "Columbo" SS Brakes, '850 FD, ACCT
                  1979 XS1100SF: "Bush" W.I.P.
                  1979 XS1100F: parts
                  2018 Heritage Softail Classic 117 FLHCS SE: "Nanuk" It's DEAD, it's not just resting. It is an EX cycle.
                  ♬
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