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2001 Yamaha 0X66 200 hp fuel issues

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  • 2001 Yamaha 0X66 200 hp fuel issues

    Hello everyone I purchased this boat about 2 years ago and the motor has ran like a top until this past weekend. It started with not wanting to crank unless it has almost full throttle. This is a fuel injected motor and never needed more than just pressing the choke to get it started on a cold start. Today I gave it a basic tune up. New Plugs, Impeller, also ran injector cleaner through the motor with a little less than a gallon of gas. While running the cleaner through the system I noticed tons of fuel coming from the prop area. It went through the entire gallon of gas in about 2 minutes. I checked the fuel pressure and it was 35 psi on idle. If I turn the motor off and pump the bulb gas starts leaking from the exhaust,prop area and I have to give it full throttle to get it started. It is almost like something is stuck open and pouring gas into the cylinders. I took the breather off and pumped the bulb and from what I could tell all the throttle bodies looked the same and no injectors were leaking and I could not tell where the gas is coming from. I am leaning towards the lower pressure pump but really not sure what to troubleshoot next. Any help will be greatly appreciated.

  • #2
    fuel injected motors do not have chokes, .
    to much pressure or stuck injector is what I would be looking for.
    But if this motor has lift pumps running on crankcase pulses then I would look there too

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    • #3
      If the fuel pump diaphragm has failed then gasoline will be pumped into the motor when the primer ball is squeezed. Gasoline may very well come out of the exhaust.

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      • #4
        I am about to go out and recheck everything now. It has 2 low pressure pumps that feed the high pressure pump. I am suspecting one of the low pressure pumps is the issue. I had to remove the check valve in the tank fitting at the lake to even get it to pump last weekend.

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        • #5
          I took off the high pressure pump and split the fuel vapor separator and everything seemed to check out fine. The float is working properly so the only way for I see for the fuel to get into the motor is from a stuck open injector. What the best way to tell which injector is the problem? I also see online where people talk about the 2 low pressure pumps torn diaphragms causing issue with flooding but by looking at the diagram i see no way for it to get into the motor except through the injectors? Any help will be greatly appreciated.

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          • #6
            the lift pumps work off of crankcase pulses, if they leak the fuel will go direct into the crankcase

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            • #7
              I hear what your saying but I don't see or understand how. The only vacuum line I am seeing is hooked to the fuel pressure regulator I checked its line and it seemed clean. I must be totally missing something. I know with my old Johnson it had a vacuum line directly connected the the pump that went to the block. I am not seeing that on the Yamahas, Can you explain how these pumps get their pulse? Thanks in advance.

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              • #8
                the pumps are bolted onto the pulse ports(Holes in block), there is a gasket sealing that connection

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                • #9
                  Ok. I see the light now. That has to be my freaking problem. I am going to replace both pumps. I am assuming the new pumps will come with the gaskets and everything I need?

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                  • #10
                    Thanks everyone. This weekend I installed 2 new low pressure pumps. The top one was leaking. I also put in new plugs,new impeller,cleaned the 02 sensor, and cleaned high pressure tank filer and she fired up and ran like a champ. Thanks for all the help. I now just need more time to hit the lake.

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                    • #11
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                      Thanks everyone. This weekend I installed 2 new low pressure pumps. The top one was leaking. I also put in new plugs,new impeller,cleaned the 02 sensor, and cleaned high pressure tank filer and she fired up and ran like a champ. Thanks for all the help. I now just need more time to hit the lake.
                      Last edited by jstatham; October 9th, 2017, 09:34 AM. Reason: https://www.youtube.com/watch?v=rv_p0wpY1gs

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