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Knowing when to replace the old fuel pump

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    Knowing when to replace the old fuel pump

    The pump is located in the RH tank and its returning fuel pipe helps to siphon the fuel from the LH tank into the RH tank, when it is running healthy. However when the old pump is worn and weaker, it might still be able to supply the required pressure but barely, and so not a whole lot of extra fuel returning back to the tank and this slows down the siphon rate even to nothing. So now the LH tank might have a lot more fuel than the RH tank.
    So, to check the condition of the pump, we just need to use INPA or the dash hidden display to show the fuel left in the tanks when the gauge showing low. I had a low fuel light today and INPA showing about 2 gal for each tank which is good. If it shown 15 gal on the left and 2 gal on the right then I should be worried.

    #2
    Want to know when to replace the fuel pump? Drive your car until the pump just gives up and you get stranded in the middle of a busy street. Ask how I know lol

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      #3
      Originally posted by erickhoyos View Post
      Want to know when to replace the fuel pump? Drive your car until the pump just gives up and you get stranded in the middle of a busy street. Ask how I know lol
      Yuuuuup

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      2002 Topasblau M3 - Coupe - 6MT - Karbonius CSL Airbox - MSS54HP Conversion - Kassel MAP - SSV1 - HJS - PCS Tune - Beisan - MK60 Swap - ZCP Rack - Nogaros - AutoSolutions - 996 Brembos - Slon - CMP - VinceBar - Koni - Eibach - BlueBus - Journal

      2012 Alpinweiss 128i - Coupe - 6AT - Slicktop - Manual Seats - Daily - Journal

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        #4
        Just replace it, fuel pumps are a wear item. Get an upgraded one and then you can do fun stuff like run E85 for easy gains and cheaper cost per mile.
        Instagram: @logicalconclusion

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          #5
          You may be able to sense it going out like it did for me, trouble starting and would die at idle the day before it finally stopped altogether. Luckily, I limped home before it fully quit.
          DD: /// 2011.5 Jerez/bamboo E90 M3 · DCT · Slicktop · Instagram
          /// 2004 Silvergrey M3 · Coupe · 6spd · Slicktop · zero options
          More info: https://nam3forum.com/forums/forum/m...os-supersprint

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            #6
            If your vacuum system is in good condition and if your car very slightly bounces at idle, it's likely the fuel pump slowly failing. I had this issue and once I replaced the pump, the car idled dead smooth. You can also check if the pressure is within spec to see if it's slowly failing.

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              #7
              What kind of life, in terms of mileage, were you all getting before failure? Wondering if it's like the regular e46 fuel pumps that typically fail ~100k - 110k miles.

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                #8
                I was able to save myself home with a hammer

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                  #9
                  Originally posted by Will View Post
                  What kind of life, in terms of mileage, were you all getting before failure? Wondering if it's like the regular e46 fuel pumps that typically fail ~100k - 110k miles.
                  Mine failed at 119,092 mi
                  2002 Topasblau M3 - Coupe - 6MT - Karbonius CSL Airbox - MSS54HP Conversion - Kassel MAP - SSV1 - HJS - PCS Tune - Beisan - MK60 Swap - ZCP Rack - Nogaros - AutoSolutions - 996 Brembos - Slon - CMP - VinceBar - Koni - Eibach - BlueBus - Journal

                  2012 Alpinweiss 128i - Coupe - 6AT - Slicktop - Manual Seats - Daily - Journal

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                    #10
                    Originally posted by Will View Post
                    What kind of life, in terms of mileage, were you all getting before failure? Wondering if it's like the regular e46 fuel pumps that typically fail ~100k - 110k miles.
                    Just to give you an idea... When I replaced my fuel pump last month, it was fully original, manufactured the same month as my car. It had 224k miles on it.
                    Instagram: @logicalconclusion

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                      #11
                      Originally posted by enjoy_m3 View Post
                      IYou can also check if the pressure is within spec to see if it's slowly failing.
                      Easy to check the hidden display than hook up the fuel gauge.

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                        #12
                        I replaced mine when the car started struggling to start. Apparently this is/was a common issue. As for mileage, it only had 42k, but the pump was now 19 years old. replaced it with a new OEM and its been smooth sailing since.

                        Sent from my SM-G960U using Tapatalk
                        Last edited by Cbouts; 03-09-2021, 09:46 AM.

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                          #13
                          Originally posted by Cbouts View Post
                          I replaced mine when the car started struggling to start. Apparently this is/was a common issue. As for mileage, it only had 42k, but the pump was now 19 years old. replaced it with a new OEM and its been smooth sailing since.
                          That’s the internal check valve. Goes out early when cars sit and moisture in tank ruins it.
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                            #14
                            Originally posted by Cbouts View Post
                            I replaced mine when the car started struggling to start. Apparently this is/was a common issue. As for mileage, it only had 42k, but the pump was now 19 years old. replaced it with a new OEM and its been smooth sailing since.

                            Sent from my SM-G960U using Tapatalk
                            If you still have that 42K bad pump, I would love to investigate what's wrong.

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                              #15
                              Thank you for this. Mine went out this morning. Will be swapping it out with OEM tomorrow upon NDA delivery. Luckily she went out approximately 1 mile from the house.

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