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Thread: Fuel Level Sending Unit Confusion

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  1. #1
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    Fuel Level Sending Unit Confusion

    Greetings,

    I have just purchased a new to me 2003 R1150RT.

    I have found the fuel level indicator on the RID unit to be somewhat unreliable. On my first trip I noticed that it only dropped about two bars and then no change. But later on the ride I noticed that the indicator started working, and I watched the bars, now indicating lower, light up and go away as I went down a pretty good hill and back up the other side. After we stopped for a break it was back to the original two bars down. I have not run the tank down far enough to get a low fuel light as yet.

    I have both a Haynes and a Clymer book and in looking in them they show a float type indicator attached to the pump filter assembly. When I go to the online parts fisch, It shows an additional tube type sender that attaches from the top of the tank. This sender is not indicated in either of these two books.

    So, what do I have? And then what can I do to fix it? I am coming off of a K1100 and it is an entirely different animal.

    Thanks
    Rod

  2. #2
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    It is a resistor sender. Often the arm gets bent from changing the fuel filter. Also the connector for the tank electrical is not sealed, and may get intermittent. Some dielectric silicone may help it.

    Rod

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    Quote Originally Posted by rkildu View Post
    And then what can I do to fix it?
    Honestly, I would just reset the trip meter at fillup and watch for about 280 to show up. Or just wait for the low fuel light at which point you still have about a gallon (say 40 miles).

    I'm not sure but the 1150's sensor may not be exposed to the fuel. I know it is a different technology than what I have on the 1100.

    On the 1100 it is a simple rheostat and sits exposed to the fuel. I have had erratic readings a couple of different times, and I seem to have fixed it with a "shock treatment" of a full bottle of STP Fuel System Cleaner (in the silver bottle). The fuel gauge has worked perfectly for a few years now.

    It might be worth a try.

    The sensor and float are mounted on the fuel pump plate in the tank tunnel.
    The other thing may be a separate switch for the warning light.
    I have been in there to replace the fuel filter, and it wasn't really difficult.
    Just a PITA to dig down through all the tupperware.

  4. #4
    not so retired henzilla's Avatar
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    this is for the RID fuel level on the right top of tank... on the RT. That connector pigtail plugs into fuel pump plate
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    Steve Henson
    SABMWRA MOA Club#62's Flat Fixer/ current forum moderator
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    Registered User texasmule's Avatar
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    Quote Originally Posted by henzilla View Post
    this is for the RID fuel level on the right top of tank... on the RT. That connector pigtail plugs into fuel pump plate
    I learned something new today, today wasn't a total waste...

    Thanks guys. I'll check mine. My fuel gauge never reaches "full" any longer. Fill gas to the top, and
    it still shows two bars down. A mild irritant, as I always use the trip odo as my fuel gauge.

  6. #6
    not so retired henzilla's Avatar
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    On the RT, it uses the float on the fuel pump to operate the low fuel warning as it does on all the models with that set up.

    The right front top of tank mounted tube is the float sensor for the fuel level display only used on the RT...I have seen those tubes pretty gummed up from stale fuel/moisture.
    Steve Henson
    SABMWRA MOA Club#62's Flat Fixer/ current forum moderator
    It's not the breaths you take, but the moments that take your breath away-D.Dillon/G. Strait

  7. #7
    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by henzilla View Post
    On the RT, it uses the float on the fuel pump to operate the low fuel warning as it does on all the models with that set up.

    The right front top of tank mounted tube is the float sensor for the fuel level display only used on the RT...I have seen those tubes pretty gummed up from stale fuel/moisture.

    Correct, The RT is different from other models.
    I have taken the tube apart and VERY GENTLY cleaned the resistance wire with a pinched piece of scotchbrite (sliding up and down)
    Clean the sliding contact on the float as well. RID will read correctly after that.
    Note: You have to remove the fuel pump plate and unplug the tube plug before the tube can be removed.
    Last edited by GSAddict; 11-04-2013 at 03:57 AM.
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    Recently read an interview with BMW m/c exec (do not recall his name, sorry) who stated that BMW bike fuel cell sensors are meant to only accurately measure the last half of the fuel in the cell. The sensors and gages are mostly useless until you get to about the half full (or half empty) level. That makes some sense when you consider the "interesting" shapes of the various fuel cells and how difficult it is to accurately measure the level of fuel therein. My personal observation is that the gage reading does seem meaningless until I get about 125-130 miles on a tank of fuel, then the gage begins to drop steadily with mileage until the low-fuel light comes on at somewhere around 175 miles.
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  9. #9
    Registered User arthurdent's Avatar
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    Quote Originally Posted by royce View Post
    Recently read an interview with BMW m/c exec (do not recall his name, sorry) who stated that BMW bike fuel cell sensors are meant to only accurately measure the last half of the fuel in the cell. The sensors and gages are mostly useless until you get to about the half full (or half empty) level. That makes some sense when you consider the "interesting" shapes of the various fuel cells and how difficult it is to accurately measure the level of fuel therein. My personal observation is that the gage reading does seem meaningless until I get about 125-130 miles on a tank of fuel, then the gage begins to drop steadily with mileage until the low-fuel light comes on at somewhere around 175 miles.
    This is a lot like my experiences with fuel indicator. Makes more sense than any of the other explanations I've seen in the past. (04 1150 GS)

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    Thanks for the information folks. Especially the comment about removing and cleaning the "fuel tube". I cannot find anything in my books about it at all.

    I cleaned the connector under the tank today with contact cleaner and put some dielectric grease on it. We will see. The bike apparently sat idle for a time based on what I am finding. Had a coil failure and just got that fixed, so my calculated gas mileage is probably off. I'm trying to get a feel for how many miles I can get per tank and about when the low fuel light will come on. I have an Airhead so I know about using the odometer to judge fuel, I just need a starting point.

    What would be an average MPG figure for this thing? That would also give me a starting point. My one trip I refueled 3 times and my mileage is all over the place due to the weak coil, I hope.

    Rod

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