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Buzzing/whining from fuel pump area when hot?

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    Buzzing/whining from fuel pump area when hot?

    Hey everyone, i been having a problem with my 1985 323i recently. I get a buzzing/whining noise when the car gets hot. Its driving me crazy. If the outside temp is more an 70 degrees the car develops an annoying whining noise. Its coming from under the rear seat and i have looked under the car while its buzzing. Im sure it coming from the fuel pump but i cant tell 100%. The 1985 323i have an external fuel pump only and i am thinking about replacing it. I have already replaced the fuel filter. I have no loss of performance and this has been going on for a while now. Its weird that this only happens if it is hot outside and the gas tank being full makes no difference. Has anyone had this happen before? Im not sure what to do. also i noticed sometimes when i press the clutch in the rpms's drop very quickly below idle rpm and then return to normal. Any idea what this can be as well? Thanks.

    #2
    If you are having your car parked on idle, then there is nothing else but fuel pump...
    Also you would not want it to die on you somewhere far away from home...

    Was your car maybe automatic before?

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      #3
      Fuel pumps make some heat. And usually you would never know that, because it's inside a tank of gas, and all that heat is dissipated into the fuel,and then out of the tank's metal sides.

      This is just a guess. But it sounds a lot like what some 80-90's cars would suffer from. Called "vapor lock" - if the gas lines get too hot for some reason, the pump will start to cavaiate the fuel rather then pump it. Happens a lot on air cooled VW and p-cars. Just throwing that out there.

      If you get moving down the road, does it go away?
      Originally posted by Matt-B
      hey does anyone know anyone who gets upset and makes electronics?

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        #4
        Originally posted by george graves View Post
        Fuel pumps make some heat. And usually you would never know that, because it's inside a tank of gas, and all that heat is dissipated into the fuel,and then out of the tank's metal sides.

        This is just a guess. But it sounds a lot like what some 80-90's cars would suffer from. Called "vapor lock" - if the gas lines get too hot for some reason, the pump will start to cavaiate the fuel rather then pump it. Happens a lot on air cooled VW and p-cars. Just throwing that out there.

        If you get moving down the road, does it go away?
        No, once the buzzing starts it gradually gets louder. I should have mentioned that I get a strong fuel vapor smell coming from the fuel pump area when this happens. Is there some sort of check valve that deals with fuel vapor that may have failed? Also when the ingnition is turned just before starting the fuel pump makes a weird noise. I understand it’s normal for the fuel pump to prime itself.. but as I mentioned before this only happens when the outside temp is hot. When the car is first started and I start to drive and apply the brakes the buzzing noise will suddenly appear and go away once I let off the brakes until about 20 minutes later it will start buzzing consistantly starting off very quiet to loud in the matter of 15 minutes. I’m going to swap out the fuel pump soon but I feel like it might be deeper than that. This problem just developed over the last few weeks.

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          #5
          Originally posted by cro_xt View Post
          If you are having your car parked on idle, then there is nothing else but fuel pump...
          Also you would not want it to die on you somewhere far away from home...

          Was your car maybe automatic before?
          Yea I think about the car dying on me all the time lol. It’s a 1985 323i euro model. It shares some parts with the e21 series and some with the American e30 models. The car is stock and has always been manual.

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