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Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

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  • Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

    I have a 2003 Ox66 yamaha 3.1 225 with 350 hours. I have gone through 6 mechanical fuel pumps in the last 100 hours (changed all three twice) and now today I find I have one leaking again (the middle one). The other two are fine. I am wondering what is causing this? I have heard the diaprahms on these pumps frequently fail, but am wondering if another problem is causing these failures. The motor runs good, but when a pump goes I lose top end and have to drop the throttle back and then punch it to get it back. Change the pump(s) and it is fine until the next time it happens. This is getting expensive and I would hate to blow the engine if there is another problem causing a lean fuel condition.

  • #2
    Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

    What is the complete model number of your motor? What is the part number of the pumps that you installed? Are you using external tanks? What make?

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    • #3
      Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

      The model number is VX225TLRB. 2003 225EFI Ox66 VMAX. The pump(s) I am installing is 6E5-24410-03-00. The fuel tanks are internal. Two 32 gallon tanks, with a selector switch. The fuel line runs through a water seperating filter before it gets to the engine.

      I have changed the water seperating filter annually and changed the filter on the engine last year. I also replaced the primer bulb with a genuine Yamaha bulb. I have never cleaned the VST filter. Could this be the problem? I can't find much on how the VST is cleaned while searching. I did see the seal at the top of the VST box is about 30$ to replace. Nice.

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      • #4
        Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

        running ring free?
        HUMAN BUILT = HUMAN FIXED
        CERTIFIED MARINE TECH

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        • #5
          Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

          No, I don't run ring free, but I use Yamaha combustion chamber cleaner (de-carb) once per year and run high quality oil (Merc Premium Plus) and almost exclusively use Chevron (Techron) gasoline. Can I clean the VST filter with spray type carb cleaner or do I have to buy a new filter?

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          • #6
            Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

            buy a new filter
            HUMAN BUILT = HUMAN FIXED
            CERTIFIED MARINE TECH

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            • #7
              Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

              Yes you have the correct fuel pumps. Did you change the fuel filter element with a 65L-24563-00-00 element? Where are you located? Do they use ethanol in your area? Gas with ethanol goes bad in 60 days without adding anything to it.

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              • #8
                Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                Yes, I changed it with the correct filter. I'm in Austin, TX. No ethanol here to my knowledge. I almost always use Chevron or Texaco gasoline. I have a friend that has been through nine pumps (same engine) in a few years. I am beginning to think this is just an engineering flaw with the diapraghms. I know this is a common problem with this engine. It is just strange that I go 200 hours and have no trouble, change out three, and then change three more 50 hours later and now have one more puking fuel.

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                • #9
                  Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                  Why not just replace the diaphragm instead of the entire fuel pump? The part number is 6E5-24411-00-00. All of the other parts to rebuild this pump are also available. Did you replace the fuel pump mounting gaskets when you changed the fuel pumps? The gasket is part number 650-24431-A0-00. Call up Yamaha customer service at (866) 894-1626. They open at 8:30 EST. See if they have any insight into this. Ask if there is a technical bulletin concerning this problem.

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                  • #10
                    Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                    Thanks. I also ordered a diaphragm kit ($16.00 vs 32 for complete pump), which I'll use for my next failure. The reason I haven't just replaced the diaphragm is a recommendation by Ray Neudaker (sp?). I think he posts on this board from time to time. He has always suggested replacing the whole pump.

                    Oh and yes I always replace the mounting gasket. To cheap not to.

                    Steve

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                    • #11
                      Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                      Just got off the phone with Yamaha. No service bulletin on this.

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                      • #12
                        Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                        nope no bullitens on the lift pumps other than a redesign but nothing to do with the diaphrams.
                        run much with one leaking and you will post about lean piston burn or puking rod bearings thjough.
                        the 3.1L motors are rather hard on pumps for some reason.
                        try a fuel system vacum test. use the inlet at the lower pump. vacum should be less than 6"Hg at WOT, I would rather see about 4"Hg.
                        anything more and you have a restriction.
                        if the check valve is still between the fuel filter and the pump inlet then remove it.
                        no your VST has nothing to do with bad lift pumps.
                        is the diaphram disentagrating or just tearing?
                        no tech questions by PM, they wont get answered.
                        you have to be trusted by the people that you lie to .

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                        • #13
                          Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                          The last ones that leaked I took apart and looked and really didn't see anything dramatic. I am thinking they must be pin hole leaks. This newest failure I'll take apart and look very carefully. When I remove that check valve won't that siphon gas back to the tank? Ah, the tank should have a check valve. Once I remove that valve I assume a standard piece of fuel line will work?

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                          • #14
                            Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                            The check valve is still there.
                            Last edited by Basser1; December 29th, 2007, 10:09 PM. Reason: Double posted

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                            • #15
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                              Re: Yamaha 3.1 225 EFI Fuel Pumps_why are the diaphragms going out

                              Took the leaking pump off and replaced it with a new one. Took the old one apart and looked for holes, tears in the old diapraghms. Couldn't see anything that looked like a hole or tear and I held it closely to a light. Just like the last ones I replaced. I'm a little baffled, other than thinking the gas is weeping through the diaphragm membrane. Any thoughts from those in the know?

                              I'm still wondering if removing the check valve is really somthing I should do.

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