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Problem solvers

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  • Problem solvers

    Been on this for 3 days and totally giving up.
    20'er with a 4.3. Everything runs great. Engine is perfect. Fuel is clean. Fuel filter is new. Running on the tank, it only gets 3 lbs of fuel pressure. Running on a separate tank, 7 lbs. Changed the pickups, took the tank out and cleaned it. Was not dirty. I take the pickup out of the tank and put it into a 5 gal can and it has 7 lbs pressure, so it has to be the tank, right? Vent tube clear. Actually disconnected. TANK IS CLEAN. I give up. unless someone comes up with a solution, I'm putting a tank on the deck.
    Thanks, jerry
    1988 26' cuddy
    1975 20' open
    16' Sandpiper
    14' Certified Fiberglass

  • #2
    Air being sucked somewhere. Line, fitting or hose.
    Atlantic City, NJ
    1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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    • #3
      I remove the pickup from tank and place it in can, go from 3 to 7 PSI. Nothing in the line is changed.
      1988 26' cuddy
      1975 20' open
      16' Sandpiper
      14' Certified Fiberglass

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      • #4
        Run a clear hose with a loop in it after the pump and see if you are getting air. Your 5 gallon can is probably higher than the pump so it is siphoning. With the fuel in the tank it is drawing whatever is easiest. Air is easier than fuel.
        1980 pilot house 351
        1988 260 predator 408

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        • #5
          Steve, that makes sense. Will do. Thanks. Skip, now I understand.
          1988 26' cuddy
          1975 20' open
          16' Sandpiper
          14' Certified Fiberglass

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          • #6
            Anti siphon check valve on tank clogged or stuck?

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            • #7
              I had a pickup tube that was hitting the bottom of the tank .It was a 3 day deal also.
              20' PH several modifications'

              17 Irvette IB V8 gm

              26 Ranger Tug diesel

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              • #8
                Any rubber fuel lines possibly collapsing?

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                • #9
                  No anti siphon valve and pick up tube is good. Changed all the hoses.
                  Today I changed out the whole filter assembly. Ran for about 3 minutes at 7 PSI then slowly dropped off. Brought the RPMs up to 4500 for about 30 sec and back to 7 psi for about 15 sec and then back to 3 PSI. Took a break, another story, and started it up about an hour later. Ran at 7 for about 10 minutes. Putting it in the water tomorrow.
                  1988 26' cuddy
                  1975 20' open
                  16' Sandpiper
                  14' Certified Fiberglass

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                  • #10
                    Fuel pump is petering out.
                    1980 pilot house 351
                    1988 260 predator 408

                    Comment


                    • #11

                      Any metal lines between tank and pump. Possibly rust buildup blow it out backwards from pump to tank into a rag to catch anything that comes out to see.

                      Is the pump mechanical or electric. Is there a screen in the inlet hose barb to the pump ,outlet barb too. I’ve seen some electrical pumps have screens internal.

                      1982 20' Cuddy
                      Boynton built

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                      • #12
                        New Carter electric pump. No screen on anything. No metal lines. When I first installed this engine, the pump was flooding the Quadrajet. I installed a fuel pressure regulator and gauge. Now this.
                        Tank, P/U, fuel filter, fuel pump, floscan[doesn't work], regulator, gauge and carb.
                        1988 26' cuddy
                        1975 20' open
                        16' Sandpiper
                        14' Certified Fiberglass

                        Comment


                        • GREGK
                          GREGK commented
                          Editing a comment
                          Did You try to turn up the pressure when on the tank in the boat? Maybe something in the regulator?
                          3 lbs of pressure is ok if the pump keeps the carb filled. Max 7.5 on a q jet
                          Take the tank with you and run it, if it stays between 3-7 and don’t bog down or go to 0 you may be looking at it to deep?
                          Wish l was there to help. It’s so much easier in person to check and not guess.

                      • #13
                        Amen Greg!!! When Jerry first posted, I didn't even think about a regulator.
                        Fluid regulators are usually based on a spring with a certain amount of give to and from if the pressure on one side of the spring is greater it will increase if the pressure on the other side of the spring is acting as a vacuum it will be less so it will actually fluctuate. The amount of fluctuation is usually preset.
                        Last edited by Ship; 04-18-2020, 06:39 AM.
                        Atlantic City, NJ
                        1982 Cuddy, Rebuilt 351 .060 rings, Edelbrock carb

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                        • #14
                          Did you pressure test the tank? Blow it up with a hand pump or a couple of pounds of air and see if it holds pressure
                          '78 20ft Cuddy
                          Mercruiser 350 FWC preVortec w/Carb

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                          • #15
                            Just because the fuel pump is new, could still be faulty. One of the valves inside may be leaking back.

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