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Thread: fuel from only one tank??

  1. #1
    wet77
    Took the boat out today and have the new mallory pump with BYPASS regulator and I noticed I was pulling all the fuel from one tank??
    Here is the setup
    All hoses are 8an
    2 lines one from each tank same length to filter
    1 line out of filter to pump
    pump to regulator
    regulator to carb manifold
    return out regulator to a T then equal lines to front of each tank.
    I just noticed this problem today have not tried to troublshoot it yet I thought I would throw it out there and see if anyone has any ideas right away maybe its my setup?
    pump worked fine its the second time out and I noticed I only got to 5700rpm today the first time out was 6100 rpm??
    It is very hot out here about 94 today and it was maybe 81 when I first tried the boat, can temp make that much difference?? :2purples:

  2. #2
    SmokinLowriderSS
    It is possible for the heat to make that much, yes.

  3. #3
    Senior Member
    Join Date
    Feb 2009
    Posts
    2,626
    return out regulator to a T then equal lines to front of each tank.
    Could have saved a lot of plumbing work by simply running the return back into the supply going to the pump.

  4. #4
    Shark In The Pond
    I had that problem once and found that one of the pick up's had some trash in it . I took the lines off from T and blew back through them and found the problem ? Not saying it is the problem but maybe something to check ?

  5. #5
    atxwrangler
    if you block in the one tank, which it pulls out of first,is the performance the same? pluggage can cause the loss of fuel and the boat may run fine for a short wide open throttle run, but will choke or die when motor runs out of fuel.i had a boat with trash in one tank, speaking with experience. :skull:

  6. #6
    Heatseeker
    Another thing you might check is the tank vents. A blocked vent could slow down the flow from a tank.

  7. #7
    wet77
    Another thing you might check is the tank vents. A blocked vent could slow down the flow from a tank.
    I think my tanks vent through the caps??
    eliminator daytona with 23 gal. stainless tanks in the tunnels in back.
    power loss I think was part the heat and other I just found out a minute ago the lash on my mechanicl roller loosened up :hammerhea
    going to try to set the lash Sunday first time since its been off the dyno,
    have about 2-3 hours of run time, is that normal??

  8. #8
    Old Guy
    I suspect that you have air in the fuel line of the tank that isn't feeding properly.
    If you remove the filter and put something there to catch the fuel, then put a SMALL amount of air pressure in the tank that isn't working, it should fill the line with fuel. If both lines are completely full of fuel, the pump should draw from both tanks.
    Of course, if you have a plugged line (I doubt it), little if any fuel will come out when you apply pressure to the tank.
    You may need help to cover the vent and fuel fill while you apply air pressure to the return line at the front of the tank.
    It is EXTREEMLY important that only a very SMALL amount of air pressure is used. It doesn't take much to destroy some fuel tanks.
    This is something that I have done many times to get the air out of the lines on a new fuel system.
    I agree with Oldsquirt. Your system will be simpler and probably work better if you bring a single return line from your regulator back to a point just before the pump. I know the instructions say to "return to tank". It isn't really necessary. Just ahead of the pump works just fine.

  9. #9
    wet77
    I suspect that you have air in the fuel line of the tank that isn't feeding properly.
    If you remove the filter and put something there to catch the fuel, then put a SMALL amount of air pressure in the tank that isn't working, it should fill the line with fuel. If both lines are completely full of fuel, the pump should draw from both tanks.
    Of course, if you have a plugged line (I doubt it), little if any fuel will come out when you apply pressure to the tank.
    You may need help to cover the vent and fuel fill while you apply air pressure to the return line at the front of the tank.
    It is EXTREEMLY important that only a very SMALL amount of air pressure is used. It doesn't take much to destroy some fuel tanks.
    This is something that I have done many times to get the air out of the lines on a new fuel system.
    I agree with Oldsquirt. Your system will be simpler and probably work better if you bring a single return line from your regulator back to a point just before the pump. I know the instructions say to "return to tank". It isn't really necessary. Just ahead of the pump works just fine.
    Nothing obstructing the tank blew in the line and got back a face full of gas :hammerhea
    If I open the gas caps and turn on the pump I here fuel returning to both tanks :wink:
    Will try to get all the air out this time and try running it again Sunday.
    I was not sure if returning to the in on the pump would work so I returned to the tanks instead.
    Also spent $340 in earls fittings and hose in the process :hammerhea
    Live and learn at least I was out for one hour today and the electric pump did not die this time :wink:

  10. #10
    sdba069
    i've never trusted a "hope they will equalize fuel system". valve it. Spend the big money on the SF-100 electric tank valve or get the nice high flow billet one. Don't know how many times I've heard, oh they pull the same, then end up rescueing them up the river with one empty tank and one full tank and can't pump an ounce of gas. Nothing like a good set of needle nose vice grips to squeeze off a line to the empty tank. Clamp it off, turn on the fuel pump, and what do you know, you have fuel again. Then there's the guy who welds fittings in the tanks for bottom pickup, then runs the equalizer line up and over the pump inside the transom, which is higher than his fuel and wonders why his tanks won't equalize.

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