1. Welcome to Tundras.com!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Tundra discussion topics
    • Transfer over your build thread from a different forum to this one
    • Communicate privately with other Tundra owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

Fuel gauge acting weird....where should I start looking?

Discussion in '1st Gen Tundras (2000-2006)' started by Aerindel, Aug 2, 2022.

  1. Aug 2, 2022 at 2:31 PM
    #1
    Aerindel

    Aerindel [OP] New Member

    Joined:
    Jan 31, 2019
    Member:
    #25399
    Messages:
    1,180
    Gender:
    Male
    Montana
    Vehicle:
    2000 Tundra AC, SR5, 4.7 V8 4WD, 325,00ish miles.
    The other day I fueled up my truck (ouch) and on the way home noticed my tank was readying down almost 1/4 after only driving 18 miles. I stopped and checked for fuel leaks but found nothing and figured that maybe the fuel nozzle just clicked off without fueling the tank all the way and I didn't notice.

    About a week later, I am driving the truck again and I see the fuel gauge is now below 3/4s after only 22 miles total...and right before my eyes, I see it creep slowly to half....then, a minute later, it slowly rises up to just below full... the correct reading based on actual milage.

    Do we suspect it's the gauge cluster failing or the sender? Is there any way to test?
     
  2. Aug 2, 2022 at 2:34 PM
    #2
    KNABORES

    KNABORES Elitist forum troll

    Joined:
    Jan 1, 2020
    Member:
    #40572
    Messages:
    3,372
    Gender:
    Male
    Arkansas
    Vehicle:
    2000 Limited TRD AC 4X4 Thunder Grey. 2019 Limited TRD CM 4x4 Cement Grey
    2000: Bilstein 5100's 16x8 589's with 265/75/16 and 1.25" spacers Flowmaster 50 series over the axle dump Westin bull bar with 20" LED Pioneer touchscreen with backup camera Full interior and dash LED conversion Trailer brake controller with 7 pin Bedliner coat bumpers trim and tool box 2019: ARE topper with full Bedrug kit and Vortex rack TRD shifter Red tow hooks for that +15 grip bonus
    Mine does that. I’m assuming it’s the sending unit. In the gas tank.
     
    FrenchToasty likes this.
  3. Aug 2, 2022 at 2:42 PM
    #3
    shifty`

    shifty` trying to remember when but it makes me dizzy

    Joined:
    Jun 20, 2020
    Member:
    #48239
    Messages:
    6,447
    ATL
    Vehicle:
    '06 AC Limited 4WD + LSD & TOW PKG
    Yes. Almost all modern tanks use a float system with variable resistance as the float moves up and down its post.

    You can measure the resistance on the float at the known tank level using a DMM. Not sure about testing the gauge, but I'm sure you could probably look at FSM for the resistance range and feed the gauge resistance across that spectrum of values to see if it sweeps right.

    Could just be your float was temporarily stuck.
     
    Last edited: Aug 2, 2022
  4. Aug 2, 2022 at 2:54 PM
    #4
    BubbaW

    BubbaW Saw it right off

    Joined:
    Aug 19, 2019
    Member:
    #34845
    Messages:
    2,320
    First Name:
    Bubba
    Vehicle:
    04 DC LTD 4X4 4.7 V8 DOHC
    T150 Fan
    Testing the sender is one test. For your year, pin 1(Blk/Red) & 2(Yel/Red). With your roughly full tank, you should see Approx 3 Ohms.

    Fuel Sender.jpg
     
    Aerindel [OP] likes this.
  5. Aug 2, 2022 at 2:57 PM
    #5
    KNABORES

    KNABORES Elitist forum troll

    Joined:
    Jan 1, 2020
    Member:
    #40572
    Messages:
    3,372
    Gender:
    Male
    Arkansas
    Vehicle:
    2000 Limited TRD AC 4X4 Thunder Grey. 2019 Limited TRD CM 4x4 Cement Grey
    2000: Bilstein 5100's 16x8 589's with 265/75/16 and 1.25" spacers Flowmaster 50 series over the axle dump Westin bull bar with 20" LED Pioneer touchscreen with backup camera Full interior and dash LED conversion Trailer brake controller with 7 pin Bedliner coat bumpers trim and tool box 2019: ARE topper with full Bedrug kit and Vortex rack TRD shifter Red tow hooks for that +15 grip bonus
    Trouble with mine is it’s intermittently faulty
     
  6. Aug 2, 2022 at 3:05 PM
    #6
    shifty`

    shifty` trying to remember when but it makes me dizzy

    Joined:
    Jun 20, 2020
    Member:
    #48239
    Messages:
    6,447
    ATL
    Vehicle:
    '06 AC Limited 4WD + LSD & TOW PKG
    I haven't seen any of the pumps out of our trucks in person yet. Many I've changed in the past have a simple steel slide the float travels up and down on. Some have a magnet in the float itself I've heard of corrosion, and even tank floaters getting jammed in the float.

    But it's also possible there's a dirty trace on the back of the gauge, or with how tasty the fuel lines at the filler neck are, and the wiring sheaths, could be rodents ate through. Tough to say.

    Best option is, when you see the gauge registering way lower than expected, test the resistance on the float/sender combo. I can't explain how to do it, though. Just that it should be possible.
     
  7. Aug 2, 2022 at 3:23 PM
    #7
    tokolosh

    tokolosh Serial procrastinator

    Joined:
    May 20, 2021
    Member:
    #63313
    Messages:
    83
    Gender:
    Male
    First Name:
    J
    SF Bay Area
    Vehicle:
    05 AC V8 SR5 Phantom Grey
    new driver
    I wonder if any of this relates to mine? Mine seems to drop normally till just below 1/4 left and then stops moving. I ran out of gas a few months back because I thought I still had almost a quarter tank left
     
  8. Aug 2, 2022 at 4:00 PM
    #8
    shifty`

    shifty` trying to remember when but it makes me dizzy

    Joined:
    Jun 20, 2020
    Member:
    #48239
    Messages:
    6,447
    ATL
    Vehicle:
    '06 AC Limited 4WD + LSD & TOW PKG
    Crappy part is, I don't think I've seen a single modern setup where the sender isn't integrated with the fuel pump, so removal for trucks means popping off the bed or dropping the tank.
     
    tokolosh likes this.
  9. Aug 2, 2022 at 10:16 PM
    #9
    Aerindel

    Aerindel [OP] New Member

    Joined:
    Jan 31, 2019
    Member:
    #25399
    Messages:
    1,180
    Gender:
    Male
    Montana
    Vehicle:
    2000 Tundra AC, SR5, 4.7 V8 4WD, 325,00ish miles.
    Yes, it's a float arm that slides across contacts on a printed board,I replaced the fuel pump last winter and got a good look at it.

    A stuck float doesn't make sense though...because I watched the needle on the gauge drop to half a tank, from 3/4s, on what was almost a full tank. A stuck float would read higher than what it was as the fuel level dropped, or stay stuck low after refilling....this showed the level actually dropping by almost half a tank, and then going back up.
     
  10. Aug 2, 2022 at 10:35 PM
    #10
    NickB_01TRD

    NickB_01TRD You don't need less cars, just more driveway.

    Joined:
    Jun 16, 2021
    Member:
    #64346
    Messages:
    1,080
    Gender:
    Male
    First Name:
    Nick
    KY
    Vehicle:
    01 Tundra SR5 TRD AC
  11. Aug 3, 2022 at 5:18 AM
    #11
    shifty`

    shifty` trying to remember when but it makes me dizzy

    Joined:
    Jun 20, 2020
    Member:
    #48239
    Messages:
    6,447
    ATL
    Vehicle:
    '06 AC Limited 4WD + LSD & TOW PKG
    True, that specific case sounds more like a wiring/power issue, or a bad/failing sender to me.
     
  12. Aug 3, 2022 at 5:51 AM
    #12
    kgsweb

    kgsweb New Member

    Joined:
    Feb 4, 2022
    Member:
    #74144
    Messages:
    5
    Gender:
    Male
    First Name:
    Greg
    My 2000 Access Cab V8 did the same thing several years ago with the fuel gauge going up and down slowly and randomly. It probably did it 4 or 5 times over several weeks. I would also smell gasoline when I would get out of the truck. Given that you likely have to lift the box off to get to the fuel tank, I did not jump right into fixing it. It's now been several years since this happened and it has not happened again.

    I guess it fixed itself.....
     
  13. Aug 3, 2022 at 2:17 PM
    #13
    Aerindel

    Aerindel [OP] New Member

    Joined:
    Jan 31, 2019
    Member:
    #25399
    Messages:
    1,180
    Gender:
    Male
    Montana
    Vehicle:
    2000 Tundra AC, SR5, 4.7 V8 4WD, 325,00ish miles.
    On an access cab you have to drop the tank, the fuel tank access port is actually under our cab, not our bed. I guess I will wait and see if it happens again.
     
  14. Aug 3, 2022 at 2:37 PM
    #14
    shifty`

    shifty` trying to remember when but it makes me dizzy

    Joined:
    Jun 20, 2020
    Member:
    #48239
    Messages:
    6,447
    ATL
    Vehicle:
    '06 AC Limited 4WD + LSD & TOW PKG
    I noticed while looking at diagrams for an '02 for another member, there was two separate part numbers for a "Fuel Sender" which were not part of the pump. Is the sending unit separated from the fuel pump on some years? Most modern trucks I've owned and changed FP out on had it integrated. Knock on wood, haven't had to do my 1GT yet.
     
  15. Aug 3, 2022 at 3:22 PM
    #15
    Aerindel

    Aerindel [OP] New Member

    Joined:
    Jan 31, 2019
    Member:
    #25399
    Messages:
    1,180
    Gender:
    Male
    Montana
    Vehicle:
    2000 Tundra AC, SR5, 4.7 V8 4WD, 325,00ish miles.
    Yes, the pump is a separate part, on the 2000's at least, which attaches to a plastic 'chassis' which has the sender on it. The pump itself is fairly cheap, even OEM. The sender unit much less so.
     
  16. Aug 4, 2022 at 1:54 PM
    #16
    Hooptytrix

    Hooptytrix Squeaky Chicken

    Joined:
    Nov 12, 2016
    Member:
    #5179
    Messages:
    1,612
    Gender:
    Male
    Dirty South
    Vehicle:
    2000 AC 4x4, 2001 AC 4x4 Sold. 2005 DC SR5 2WD
    I think your truck has a rare case of sticker shock, 1 look at the gas prices and the old girl went into convulsions.
     
    Eagleye and Aerindel [OP] like this.
  17. Sep 18, 2022 at 1:19 PM
    #17
    Aerindel

    Aerindel [OP] New Member

    Joined:
    Jan 31, 2019
    Member:
    #25399
    Messages:
    1,180
    Gender:
    Male
    Montana
    Vehicle:
    2000 Tundra AC, SR5, 4.7 V8 4WD, 325,00ish miles.
    Well, I think I figured it out.

    After running a few tanks through it, I find the same behavior, at the same point in the fuel gauge.

    My theory is that there is a dead spot in the sender, and when the fuel level reaches that point ( at about 7/8ths) of a tank, it gets no signal, and takes that to mean no fuel, so the needle starts dropping, until the fuel level falls, or the truck tilts, etc, to get past the dead spot on the sensor and then it acts normally afterwards.
     
    bmf4069 and shifty` like this.
  18. Sep 18, 2022 at 2:04 PM
    #18
    shifty`

    shifty` trying to remember when but it makes me dizzy

    Joined:
    Jun 20, 2020
    Member:
    #48239
    Messages:
    6,447
    ATL
    Vehicle:
    '06 AC Limited 4WD + LSD & TOW PKG
    Any chance you can emulate the condition, but filling ~7/8 tank, then jacking up either side of the vehicle to shift the fuel load in a way that would make it register +/- a couple of gallons and watch if the needle drops out, then comes back up?

    Would suck if it's a bad sender, if the sender is integrated into the pump as someone else may've eluded to.
     
  19. Sep 19, 2022 at 4:01 AM
    #19
    Aerindel

    Aerindel [OP] New Member

    Joined:
    Jan 31, 2019
    Member:
    #25399
    Messages:
    1,180
    Gender:
    Male
    Montana
    Vehicle:
    2000 Tundra AC, SR5, 4.7 V8 4WD, 325,00ish miles.
    Sender is absolutely part of the fuel pump 'chassis', I had it out last winter to replace the fuel pump, which is a separate part, but all part of the same assembly, and the sender part is a lot more expensive than the fuel pump part.

    And yes, I could do that fairly easily. I live on a steep hill so I can tilt the truck by 15º front to back just by moving it a few feet one way or another. Good idea.
     

Products Discussed in

To Top