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something restrictive in the gas tank

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    something restrictive in the gas tank

    Hey i don't know if this is the right section but here's my problem.


    i'm FI and need a big walbro 450 pump.
    fuel pressure would be 60psi, 70psi with the car running at idle.

    so i got an aftermarket FPR but it does the same thing.


    i unhooked the return at the tank and it will idle at 30psi so looks like the FPR is working
    and the tank is the actual problem.


    with the walbro 255 this was not a problem.

    i blew compressed air directly into the tank and that didn't help.
    thought there could be a clog or something.


    have any of you guys ever heard of this?


    also theres this weird thing in my tank i'm thinking that could be the problem?


    This is the return that goes in from the driver side and exits in the surge bowl next to the pump. I even blew air into the exit. nothing. don't think its a blockage. or maybe it's blocked so hard air won't work.



    OMG why by jet jones, on Flickr

    #2
    Originally posted by LowR3V'in View Post

    also theres this weird thing in my tank i'm thinking that could be the problem?
    Pretty sure this is the cross over line (if this is a late model tank). As far as I understand, late model tanks use some sort of eductor/venturi setup to pull gas from one side to the other instead of the "s" pipe on early tanks.

    Take this with a massive grain of salt, but maybe it uses the return fuel as the motive liquid to create suction? If it does, that could create resistance in the return line as flow increases. Not sure how you'd get around that and still receive fuel from the other side of the tank though.
    Originally posted by priapism
    My girl don't know shit, but she bakes a mean cupcake.
    Originally posted by shameson
    Usually it's best not to know how much money you have into your e30

    Comment


      #3
      Yeah, that little hump in the line is the pickup for a venturi pump, here's a thread that shows what it looks like in detail . If undid the return line at the tank and fuel pressure returned to where it should be that's a good indication that the venturi is the restriction, maybe clogged from sucking up silt in the bottom of your fuel tank, but that tank looks clean to me. Try feeding some steel wire down the return line to unclog it, if that doesn't do it the internal line and venturi itself might just be too small for the volume of return flow you're producing with that big pump. A possible solution would be to get the sender bracket from a car with a crossover pipe style tank and split your return line between the existing venturi line and the return line fitting on the sender bracket.
      @turbovarg
      '91 318is, M20B25, T3/T04E 60 trim (15psi), megasquirt, coilovers, Z3 rack, cold AC
      [b u i l d]
      [Car of the month: April 2018]

      0c8b7c9527af628a346878feb14bf757

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        #4
        thanks for the help.
        i really wish that guy cut it open to see if there was a clog.

        what do you mean about that sender bracket thing?
        like drill a hole on the level cap and bulkhead a 5/16 fitting on there. doing a Y.
        sounds good but idk if there's any room for that.

        or maybe use an early model tank.
        this sucks.


        or should i buy a new tank and gamble it's a clog
        Last edited by LowR3V'in; 07-31-2019, 10:18 AM.

        Comment


          #5
          This part has a return tube in cars which have tanks with a crossover tube on the bottom of the tank (like mine).
          Attached Files
          @turbovarg
          '91 318is, M20B25, T3/T04E 60 trim (15psi), megasquirt, coilovers, Z3 rack, cold AC
          [b u i l d]
          [Car of the month: April 2018]

          0c8b7c9527af628a346878feb14bf757

          Comment


            #6
            oh interesting. looks like they used the same cap for the weird late model tank
            and just plugged it up. link to where i can order one?



            also i was thinking of drilling and bulkheading a 5/16 elbow on the top of the driver side tank and just Y to that one..

            Pump wire upgrayedd by jet jones, on Flickr

            Comment


              #7
              Thanks for that suggestion the 318is return fixed the issue.
              Extra return by jet jones, on Flickr
              Extra return 2 by jet jones, on Flickr

              Comment


                #8
                I know it's a low pressure return, but you didn't put hose clamps on it?
                AWD > RWD

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