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  • Boiling Fuel

    Having an issue with overheating my fuel after prolonged idle. I can drive the car no problems, but twice now (after long periods idling), i notice the fuel pressure start to drop from 40 to 35 to 30 to 25, etc. One time it actually killed the car, the other it just started to lean it out. If I let the car sit for 5 minutes fuel pressure goes right back to normal. I thought it was a dirty pre-filter, and there was a lot of crud in the pre-filter, but cleaning it did not seem to fix the issue.

    System is as follows:
    8 gallon cell
    -12 to 85micron filter
    pump
    -10 40 micron filter
    -10 to -8 y block under hood
    -8 to each rail
    -8 from each rail to reg
    -8 from reg to fuel cell

    Now, a couple of issues I see currently (trying to get a grasp on what, if any/all, should be addressed first).

    1- small fuel cell, 8 gallons means less fuel volume to dissipate heat, pump moves over 3 gallons per min, thus it is flipping the tank A LOT

    2- 40 micron post-pump filter. not sure how this one slid through the cracks, but i looked at my parts sheet and that is what I am using some how. aeromotive calls for a 10 micron. not sure if this could introduce enough restriction though (hell, it's been fine for over a year and 2500 miles). figure it needs to be changed anyway so i'll buy a 10 micron

    3- no turbo blanket and lots of under hood heat. not sure if it'd make that much of a difference, but with no turbo blanket + a/c it gets hot under there. figure the fuel is picking up a decent amount of that ambient heat.

    4- no pump speed controller, this is by advice given to me as these can fail you at the WRONG time and cost a motor (plus they are expensive).

    5- very slight leak in suction line (right at the cell where the -12 bulk head comes through), it is VERY slight, like just enough to attract dirt on the sump of the cell. i have replaced the seal at the bulk head but it still has this very slight leak. could this be constantly aerating the fuel causing cavitation in the pump?

  • #2
    In my experience with fuel injection type pressures, vapor lock hasn't been a problem. They do make inline fuel line coolers. Might be something for you to look into installing. The early mechanical injection Mercedes gas motors used a fuel cooler on the return side that was cooled by the low pressure side of the a\c system. Not practical on a car that sees track duty, but neat idea. Then ran somewhere around 80 psi if I remember correct. Not sure why the need to have it. Just something I noticed working on one about 10 years ago.


    Have you used an IR thermometer to see what the fuel cell temp is when you are having this issue. Try to get an idea of the heat being generated in the fuel at startup versus when the problem occurs.

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    • #3
      Originally posted by shumpertdavid View Post
      In my experience with fuel injection type pressures, vapor lock hasn't been a problem. They do make inline fuel line coolers. Might be something for you to look into installing. The early mechanical injection Mercedes gas motors used a fuel cooler on the return side that was cooled by the low pressure side of the a\c system. Not practical on a car that sees track duty, but neat idea. Then ran somewhere around 80 psi if I remember correct. Not sure why the need to have it. Just something I noticed working on one about 10 years ago.


      Have you used an IR thermometer to see what the fuel cell temp is when you are having this issue. Try to get an idea of the heat being generated in the fuel at startup versus when the problem occurs.
      I haven't, but I will bring my IR thermo with me next time I go out in it. I ordered a new post-pump filter (in a 10 micron) and am thinking about buying a turbo blanket for it to help keep some of the heat out of the engine bay.

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      • #4
        I vote for trying a different pump. If you shrink the cell, IMO, you could make the problem worse. I think the pump is becoming inefficient
        Ring and pinion specialist

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        • #5
          shrink the cell?

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          • #6
            Originally posted by dville_gt View Post
            shrink the cell?
            go to a smaller cell as you suggested
            Ring and pinion specialist

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            • #7
              is your return in the top of the cell or bottom...
              Originally posted by soap
              i can fix anything from a broken tractor to an aching pussy!!!

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              • #8
                Control the speed of the pump. They make controllers for a reason.

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                • #9
                  Originally posted by greenbullitt View Post
                  go to a smaller cell as you suggested
                  No, I was saying I have an 8 gallon cell currently, I don't plan to change but if I were to I'd go to a stock dumped style tank.

                  Originally posted by ktm300hater View Post
                  is your return in the top of the cell or bottom...
                  Top of the cell

                  Originally posted by juiceweezl View Post
                  Control the speed of the pump. They make controllers for a reason.
                  Meh, lots of folks getting by without, I just worry about it not powering up and leaning me out.

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                  • #10
                    when your return is in the top, it makes bubbles in the fuel. Think about a bath tub with the water running in it. Especially if your pump is pumping 3 gallons a minute
                    Originally posted by soap
                    i can fix anything from a broken tractor to an aching pussy!!!

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                    • #11
                      Originally posted by ktm300hater View Post
                      when your return is in the top, it makes bubbles in the fuel. Think about a bath tub with the water running in it. Especially if your pump is pumping 3 gallons a minute
                      ya, i am going to see if i can figure out a way to at least point the return at the side of the cell so it has to run down vs. just squirting into the body of fluid.

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                      • #12
                        What are you running for a tank vent?. If you have a pump pulling/pushing enough fuel to need a -8/10 but still running a 1/4" factory vent may be causing a vacuum in the tank.

                        When you are experiencing the problem, crack the fuel filler cap. Air rushing out or in would indicate the vent is not enough.
                        Fuck you. We're going to Costco.

                        Comment


                        • #13
                          Originally posted by kbscobravert View Post
                          What are you running for a tank vent?. If you have a pump pulling/pushing enough fuel to need a -8/10 but still running a 1/4" factory vent may be causing a vacuum in the tank.

                          When you are experiencing the problem, crack the fuel filler cap. Air rushing out or in would indicate the vent is not enough.
                          -8 bulkhead w/a rollover valve, 360* loop then through the trunk pan through a filter.

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                          • #14

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                            • #15

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