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Thread: Fuel Level Help

  1. #1

    Default Fuel Level Help

    OK I need some help here. I have the 7" Digital Dash with I/O adapter & harness. The version is 4.0.33 and the blinkers and high beams are setup & working. The fuel level is not showing properly. It shows 100 (0-100 range for dash gauge), except for when I first crank the car and it might dip to 97 and climb back up. It does not change with different fuel levels. Here's the vehicle specs and how I have it setup:

    2005 Mustang / 15 empty - 160 full (Ohms) / there are two FL wires but both read close to each other
    I have checked the ohm's at close to half (around 80 something) and full which is 160ish.
    *This part should be correct.* Hopefully someone sees my error, so I can move on to the next thing. Thanks, Mike

    0-100 RANGE
    1*X+0 MATH

    15.00 / 0.00
    24.06 / 6.67
    33.13 / 13.33
    42.19 / 20.00
    51.25 / 26.67
    60.31 / 33.33
    69.38 / 40.00
    78.44 / 46.67
    96.56 / 53.33
    105.63 / 60.00
    114.69 / 66.67
    123.75 / 73.33
    132.81 / 80.00
    141.88 / 86.67
    150.94 / 93.33
    160.00 / 100.00
    Last edited by JST4FN; 03-06-2018 at 11:25 PM.

  2. #2


    OK, you’re a little unclear. It shows 100% except when you’re cranking, and then it’s fine otherwise? So you’re setup to read 0-100% full?

  3. #3


    Sorry, I left some info out. I went back and added it there and here. My range for the dash gauge is 0-100. It shows 100 at all fuel levels (bar matches). Even if I double the range (0-200) it will stay at 100 and the bar will sit at halfway then. Hopefully that makes sense? Deleted the gauge today and reloaded with the same result.

  4. #4


    I made some head way on this. The S197 Mustang has a saddle tank and two fuel level sensors which both end up going to the dash via CAN Bus. The passenger side has a pump that feeds the driver side of the tank (main pumps) to keep it full of fuel. So basically the driver side reads high on resistance until it drops below half a tank and the passenger will read low at half a tank. I guess the OEM dash is setup to read this correctly. My thought was to merge the signals which should cut the scale in half (160-15 to 80-7.5). This does work correctly when measuring resistance, but the value on the Holley Digital Dash doesn't match. To top that off, it usually starts off low and gradually goes up in value while driving, so you're not sure what to believe. The next thing I think I will try, is make the Ohm & value displayed match and then I'll check the resistance again. I thought the blinkers were going to be hard on this car, and this was going to be easy, and it's been completely the opposite.

  5. #5


    I'm having the same issue with my sender on my 2002 Camaro. How did you come up with the calibration curve? Did you linearize the graph once you put in the First and last Ohm settings? Thanks.

  6. #6


    Yes, it's linear. I haven't driven or worked on it in a week or two. I do have a working gauge, just not reliable info yet. I may have to offset the reading to get what I want, but we'll see. I'm going to change the scale to match the Ohms, and see if I can get an idea by checking tank volume.

  7. #7


    Well I have checked the Ohms. It is getting a signal to the Digital Dash. I've messed something up in the Digital Dash on mine. Not sure what yet. I put in the Full & Empty values and then I populated the cells between. When I hit Linearize, it doesn't do anything. Weird.

  8. #8


    Mine wouldn't either. I had to do it manually, but they're in a linear step.

  9. #9


    It's weird. Mine just reads 100. When I check it with a multimeter, I'm getting a signal all the way to the adapter harness. Same everywhere. Feel like I did something wrong in the Digital Dash. Did you have to adjust the Math Channel any?

  10. #10


    I haven't touched the math yet, but I might have to. Also, when I was stuck on 100 my problem was I piggybacked my factory wiring vs cutting and sending the signal to the Holley only.

    Here's the kinda of stuff I'm dealing with. I drove my car yesterday and when I got in it to go home, the gauge read 30 (should mean 30% left). This seemed low vs the mileage from the last fill up, so I checked the resistance and it was 50 Ohms (which would match the mileage driven more). The value should've displayed close to 60, given the scale 0-100 = 7.5-80 Ohms. So I start driving home and the gauge is now in the teens. I thought it didn't fill up last time (but when I left my measured ohms was 50). I decided to fill up again just in case. At the gas station I checked resistance again before the fill up and it was 34 Ohms (seemed low) with a value of 15 shown. The value should've been 36ish. I filled it up and sure enough it only took 6 gallons (16 gal tank). The Ohms measured at full was 80, but again the value showed 81 not 100 as commanded. For some reason my value does not match the scale created vs Ohms. I don't know why yet. Right now I have to use mileage to judge my fill ups. Hopefully soon I can figure this out.

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