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Fuel tank mod

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    #16
    Just in case someone else wants to do this there are a few details that aren't visible in the picture.

    There is a piece of 3/8" Type L copper tubing soldered into the elbow inside the tank. That tube is bent to roughly follow the siphon tube and curve around the pickup cup in the bottom of the tank. The elbow is threaded into a 2x2x1/8" piece of mild steel that is pop riveted to tank and sealed with JB weld. To adapt the 3/8" copper tube to the roughly 1/2" outlet of the transfer pump I soldered half of a 1/2 barbed coupler to the 3/8" tubing.

    Because the later tanks don't have a cross over tube, you need level sensors in both sides. It is a simple matter to graft the connector in place of the connector used for the level sensor on the left side. But the body of the level sensor must be electrically isolated from pump housing for both sensors to work. I accomplished that by using a die grinder to open up opening in the pump housing, insulated the studs with short pieces of heat shrink, and used gasket material above and below the level sensor flange. A hard rubber ring about 3/32" thick around the gage tube and plastic washers work work as well, if not better. If you use a ring, a bit of sealant where it contacts the pump flange would be a good idea.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #17
      Nice fix! At the last autocross with the m30, it was starving for fuel BAD trying to come out of a long corner with 1/2-1/4 of the tank. It fell it on it's face at 4-5k rpm for almost a full second until the car was once again straight....
      Mtech1 v8 build thread - https://www.r3vlimited.com/board/sho...d.php?t=413205



      OEM v8 manual chip or dme - https://www.r3vlimited.com/board/sho....php?p=4938827

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        #18
        You should not be getting starvation at a half tank. At 1/4, probably. If you are getting starvation at a half, tank either the cross-over tube on an early tank is plugged (probably with rust) or on a later tank the siphon is not as effective as it should be because of reduced flow through the system. That can be caused by a weak pump, rust in the tank clogging the pump inlet screen, or a clogged filter.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

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          #19
          I have an early tank with no cross-over tube, it only has one hump on the passenger side, now that I think about it, it was closer to 1/4 the tank mark. The filter is recent, and there is no rust. It might be a combination or low fuel and weak pump though... (changing that soon).
          Mtech1 v8 build thread - https://www.r3vlimited.com/board/sho...d.php?t=413205



          OEM v8 manual chip or dme - https://www.r3vlimited.com/board/sho....php?p=4938827

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            #20
            What car do you have? As far as I know all early (through 8/87) cars have a cross over tube between the tank halves.
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

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              #21
              I don't know when they changed from one to another, but I've seen both kinds on the early cars. Mine is an 84 318i, and here is what the tank looks like. (coolant from the shitty m10 sprayed under the car/subframe).

              Mtech1 v8 build thread - https://www.r3vlimited.com/board/sho...d.php?t=413205



              OEM v8 manual chip or dme - https://www.r3vlimited.com/board/sho....php?p=4938827

              Comment


                #22
                It comes back to me now. It has been forever since I've seen one of those and i had forgotten all about those tanks. Other than a surge tank for the high pressure pump I don't know anything that would help in this case.
                The car makes it possible, but the driver makes it happen.
                Jim Levie, Huntsville, AL

                Comment


                  #23
                  Jim, this is great info.
                  Adam Nitti and I have been discussing this mod for a few months now, as he is going through a fuel pump a year currently. The current thought is very sporadic fuel starvation, causing an early pump failure.
                  Were you seeing these symptoms before switching over?

                  Thanks,
                  Rob

                  NASA MidSouth TT Director / GTS2 #018
                  Mods: Coastal PS Fluid, 10w40 Oil
                  Future Mods: Bosch Micro-Edge Wiper Blades, Painter's Tape, Spark Plugs, Freezer for Nutty Buddys, Adam Nitti CD's

                  Comment


                    #24
                    Anyone have any write ups on this? I would love to do this to my daily. I will do some searches, great thread guys!

                    peace

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                      #25
                      Originally posted by Airplanecar8 View Post
                      Anyone have any write ups on this? I would love to do this to my daily. I will do some searches, great thread guys!
                      A write up on what?
                      Last edited by jlevie; 04-24-2011, 07:42 AM.
                      The car makes it possible, but the driver makes it happen.
                      Jim Levie, Huntsville, AL

                      Comment


                        #26
                        would you guys know if you could fit a e36 tank on a 1990 e30?
                        I've been looking in my area for a tank but I cant find one, and I'm not looking to dish out the 600 bavauto wants....

                        I've only called a coupple scrap yards and they dont have one, but I know the E36 tank was plastic so I was thinkin in the long run this would be a better swap...

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                          #27
                          The E46 M3 has a neat little accumulator cup that sits over the pump intake and works remarkably well to limit starvation. I wonder how hard it would be to retrofit that or something similar to an E30?

                          (My 323, otoh, starves at 5/8ths f a tank.)
                          2006 GMC Sierra 2500HD 4WD LBZ/Allison
                          2002 BMW M3 Alpinweiß/Black
                          1999 323i GTS2 Alpinweiß
                          1995 M3 Dakargelb/Black
                          - S50B32/S6S420G/3.91
                          1990 325is Brilliantrot/Tan
                          1989 M3 Alpinweiß/Black

                          Hers: 1996 Porsche 911 Turbo Black/Black
                          Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

                          sigpic

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                            #28
                            An E30 tank has a cup built into it that surrounds the pump pickup, but it isn't very effective under high cornering loads.
                            The car makes it possible, but the driver makes it happen.
                            Jim Levie, Huntsville, AL

                            Comment


                              #29
                              I quess there is no foam baffles on the market that could be squeezed in,that would keep the fuel close the pump,huh?
                              NASA
                              BMWCCA member
                              PCA member 25yrs




                              1991 318IS slick top
                              1997 M3 sedan
                              2001 325CI DD

                              “whoever turns the wheel the least, wins"

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                                #30
                                You could buy some foam from Fuel Safe and just throw it in the top of your tank. They come in little cubes, easy to do.

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