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Bmw mini one - fuel gauge

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  • 04-08-2015 5:44pm
    #1
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭


    Today I got word that my girlfriend 2006 mini one is full of fuel, but the gauge (analog and digital) both say it's empty. Since its both I'm going to rule out the analog cluster as the cause. And I'm assuming is the fuel pump/fuel sender unit under the back seats.

    Any way to diagnose this?

    Is it a diy fix?

    Assuming it's the fuel sender unit, is it a whole new pump or can I swap out donor fuel sender unit parts?


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    #2
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    Black_Knight wrote: »
    Today I got word that my girlfriend 2006 mini one is full of fuel, but the gauge (analog and digital) both say it's empty. Since its both I'm going to rule out the analog cluster as the cause. And I'm assuming is the fuel pump/fuel sender unit under the back seats.

    Any way to diagnose this?

    Is it a diy fix?

    Assuming it's the fuel sender unit, is it a whole new pump or can I swap out donor fuel sender unit parts?


    This happens to hers sometimes if the car is "over" filled. Like if the pump clicks but you decide to round it up a euro or two.

    Will resolve itself once the level drops down. The solution I've come to is to just stop when it clicks, no rounding up.

    If it doesn't fix itself then there are two level sensors afaik one on the fuel filter and one on the pump. One on either side of tank under back seats.

    Edit... her car only has the dial, no lcd fuel/range info.


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    #3
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Special Circumstances wrote: »
    If it doesn't fix itself then there are two level sensors afaik one on the fuel filter and one on the pump. One on either side of tank under back seats.

    Hmmm. Previously a brimmed tank would show 3/4 full on the dial. Maybe one sensor was gone/faulty. I assume 1 sensor working and 1 failed would give a maybe 1/2 reading, so that might account for the 3/4 full reading. Am I now to believe both sensors are dead? Whats the odds of that?


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    #4
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    I'd say someone with the right levels of diagnostics should be able to get a reading from both sensors and figure out if one or both of them are dud.

    Maybe even the old "turn it off and turn it on again" battery disconnect might snap it out of whatever mood it's in????

    If you do tackle it, I would recommend removing the driver and passenger seats to give yourself room to work. (disconnect battery, careful of airbags etc).
    Leave the rear seat seat backs in place if you can at all - they are awkward to remove replace and you will probably end up scratching a load of the plastic trim in the rear side panels as your try to manouevre them. Decorate the place like Dexters kill room to stop any spills soaking into fabric.

    Pay special attention to how to get the big rubber seal right - I misread it and spent ages doing it wrong trying to get everything sealed up after a fuel filter change.


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    #5
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Thanks SC.

    Remember me?
    Black_Knight wrote: »
    Special Circumstances wrote: »
    Not a bother, I'm sure that info will benefit me, if nobody else, sooner or later.

    I've been fixing little bits and keeping an eye out for the common problems on an R50 mini for over 6 years now so shout if you have any questions.

    You can add "cracked thermostat housing" to that list. Had to get that replaced last year. Oh, and the fuel filler gauge never shows full. Most it'll go to is a bit over 3/4 full when its brimmed.


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    #6
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Any idea is this something I can do?
    http://new.minimania.com/ECU_Reset_Procedure___R50_52_53_MINIs
    Similar to this:
    http://www.bimmerforums.com/forum/showthread.php?736153-Test-Mode-Hidden-Codes-in-your-car!

    Specifically around:
    6.2 Show value of Fuel gauge.
    1= both senders OK, 2= sender failure, 3=ti signal implausible (no reading)


    Oddly, on both the links above, they mention a left and right sensor, where the left sensor has a much lower value than the right (albeit these are examples), so im wondering was it a case where my left sensor was dead (giving me 3/4 full readings) and now my right sensor is dead giving me 0 readings.


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    #7
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    I do indeed remember some of your other problems but the fuel gauge didn't register with me :-)

    Yeah very possible that you have the extra functions to do that testmode. Hers doesn't :-(

    Are you familiar with realoem.com ? Get the last section of your chassis number ( letter,letter,5digits) and you will be able to see diagrams and part numbers for your model. For the most part the dollar prices you see translate directly to euros - ie $50 becomes €50 here, + VAT (i think, not 100% about the VAT).

    I'd try to see if it was a wiring issue before jumping straight to rooting through the petrol tank. Unfortunately realoem is no good for the wiring side of things.


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    #8
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Ran the tests on the fuel sender unit. Here's the results:
    Unit recognises 17.7 liters in the left sensor, and 22liters in the right sensor
    yMS3zIJfE-OiayXYPTCeVApUUrfuhZKVEm-04XLHgqSP=w550-h971-no
    Unit can add the 2 together:
    4OW2ZxuGLdn_40ghbyhhAR171fDr-rHMrZNAqKHdSGGe=w550-h971-no

    Unit gives me a "3", signal implausible response:
    IGqOE8ZzssqpmzY7GijoiLds1BRT2bbViTiVXaAgoolx=w550-h971-no


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    #9
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    I have a feeling that when her gauge acts up I would get a "implausible" error too if I searched for it.
    The hump in the middle of the tank can cause "implausible" readings but they usually correct themselves after a bit of mileage.
    But, your setup obviously has some other issue that is adding to the usual quirks if it never reads full.

    Job for a specialist I'd say, maybe it's just a matter of recalibrating something?


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    #10
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Special Circumstances wrote: »
    Job for a specialist I'd say, maybe it's just a matter of recalibrating something?

    Hit it with a hammer you say?


    I found a case where some other guy had the same situation, he fixed it, but in the spirit of the internet he just replied saying "Turned out to be a nice easy fix in the end." and didn't explain his fix. Only other post ive found matching my situation mentions that mice had nibbled away at the wiring. Might pop off the back seat and open up the inspection ports this evening. No multimeter on me though :(


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    #11
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    Black_Knight wrote: »
    I found a case where some other guy had the same situation, he fixed it, but in the spirit of the internet he just replied saying "Turned out to be a nice easy fix in the end." and didn't explain his fix.
    L@nger...

    I assume if you're reading something other than 0% or 100% then the wiring is ok.
    Would it be a case where a support for the tank has rotted and one side has dropped - the straps don't look all that great on her car and that has a few years on yours...

    Yeah, seat base is easy* to pop off and a 10mm socket to open the covers and a big flat screwdriver to prise them up. Should be able to see the wiring for the fuel sender then... but I've never had to look at that side, only the fuel filter side. You won't need to be removing front seats to do that much.

    *Her's doesn't have isofix so it's just two clips to pop, there may be more to it for later models.


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    #12
    macplaxton
    Moderators, Motoring & Transport Moderators Posts: 2,957 Mod ✭✭✭✭macplaxton


    Have you tried turning it on and off again? :)

    Bloody computers.


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    #13
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Special Circumstances wrote: »
    L@nger...

    Yeah, seat base is easy* to pop off and a 10mm socket to open the covers and a big flat screwdriver to prise them up. Should be able to see the wiring for the fuel sender then... but I've never had to look at that side, only the fuel filter side. You won't need to be removing front seats to do that much.
    From what ive read and kinda seen, there's 2 fuel sender units in the tank. Hence the read outs of 17.7 liters the left and 22.0 liters in the right.
    macplaxton wrote: »
    Have you tried turning it on and off again? :)

    Bloody computers.

    Ive not actually disconnected the battery yet. Tonight perhaps.


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    #14
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    Black_Knight wrote: »
    From what ive read and kinda seen, there's 2 fuel sender units in the tank. Hence the read outs of 17.7 liters the left and 22.0 liters in the right.
    There are two level sensors but... you can't access anything electrical on the drivers side without removing the fuel filter canister. Edit - maybe you can, I did not have to disconnect any electrical connection on that side to take the top off the fuel filter.
    I'm guessing the wiring for both sensors comes out the fuel pump side, but maybe it comes out somewhere else?

    Hmmm, worth checking before you go routing.
    There is a workshop document here but it's a piece of crap to navigate through...
    http://wtxmc.org/MiniCooperDocs/FUEL%20SUPPLY%20COOPER.pdf


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    #15
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Think the fuel filter has to come out:
    http://www.pelicanparts.com/techarticles/MINI/17-FUEL-Fuel_Pump_and_Filter_Replacement/17-FUEL-Fuel_Pump_and_Filter_Replacement.htm
    This lies beneath I think, but I wasnt in the humour to do all that today.
    20150412_134233_zpsvmol1wdn.jpg

    I pulled the battery out after fiddling with wires (nothing much really) and now im getting a 6.2 error code 2. 2= sender failure.

    The left side (allegedly the working side) has a slightly frayed wire.
    P8aXWoCknoKSH5stgeT8z5gY3zEkcpI_2Suf3_pSnuN6=w1718-h971-no

    Might have a go at taking out the fuel filter at the weekend, see what lies beneath.


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    #16
    Special Circumstances
    Closed Accounts Posts: 7,569 ✭✭✭Special Circumstances


    Can you test them with a multimeter as is at that connector????? Not a mechanic, don't know.
    I wouldn't go ripping things for the fun of it! It really wasn't any fun doing the filter.

    If you do go at it:
    The fuel filter canister is difficult to open "in situ" as you are afraid of slipping and twisting the stuff connected underneath. But if you are taking everything out then you may as well do the filter change. About 60 euro. There are good guides on the net, billsWebspace I think is the one I followed but pelican parts has a writeup that covers pump and filter.

    I avoided pulling things out completely so didn't get a feel for how awkward it is to extract the whole unit including sensors.

    When putting things back, You must fit the big rubber seal around the lip of the tank first, then push the filter or pump down and put the metal ring back. My mistake was to to push the seal to the top of the filter unit and try to pop the seal in place by pushing it down with the fuel filter unit.

    The thread on the ring only engages at one point but it should go on fine once the seal is correct. The mallet and screwdriver method worked fine for me.


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    #17
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Seems the wiring all goes in from the fuel pump side, and routes over to the filter-side sensor within the tank, so that frayed wire may be the cause.

    If that turns out all good, it'll be a case of pulling out the filter housing (and maybe the pump) and checking for continuity along that wire. Probably check the filter-side sender unit first though.


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    #18
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Multimeter said the shoddy wiring at least has continuity through the block. The rubber bungs stop me from getting a reading while its all connected, and wasnt too sure was there much point disconnecting it and measuring since it might just error out anyways.

    From the look of the wiring, the middle brown and blue/white wires are power and earth, while the other sets of 2 are probably the fuel sender unit points. The top two (left most in the car) gave me a slightly varying resistance reading. Which the bottom 2 (right most in the car) gave me an open circuit. I suspect this is the cause for the solid 22ltrs in the right tank. The reading is sending back infinite resistance. My guess is either a disconnected wire, or a dead sender unit.

    wl2WNwhhqjBa4x7S40P4dCZOAN--YIAj6Xqs31pzpLSo=w1718-h971-no


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    #19
    Black_Knight
    Moderators Posts: 12,369 ✭✭✭✭Black_Knight


    Finally got around to doing some more DIY one this.

    I took out the fuel filter pod to reveal the fuel sender unit below. The good news is when measuring across the 2 soldiered spots I get a nice varying resistance. From here the 2 wires go into some tubing and over towards the fuel pump side of the car (all inside the fuel tank). All the connectors on the fuel filter side look grand, and I can measure resistance across them.

    So I pulled out the fuel pump side which revealed a connector block (similar to whats pictured below) for the 2 fuel sender unit wires. I have an open circuit across these 2 pins (coming from the fuel filter side). I have continuity between the corresponding pins and the connector block on top of the fuel pump (pictured in the last post).

    10-sets-2Pin-3-5mm-Auto-ABS-sensor-plug-Car-door-lamp-plug-connector-for-VW.jpg


    Seems to just be a bad wire between the left and right side of the fuel tank. Any one have a clue on a part code for this?
    If I cant replace it I think I will have to snip the bad wire, pull it out of the tank and chase it under the back seats, connect up some new wire, and down in through the fuel pump hole to the existing connector pictured above. Soldering in the fuel tank is a massive no no anyways.


    EDIT: The wire I think I need is a spade connector on one end, and the 3.5mm connector on the other side.


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