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  1. #1

    Erratic AFR readings???

    2005 RXT with X-Charger, RRFPR, Bosch 42's, Fizzle HE i/c, Graco strainer, 4" Kanaflex, Riva intake grate, Solas 15/20R, Innovate MTX-L, VTS, Riva thru hull exhaust, pump wedge, water box mod, Riva catch can, Riva block off.

    Ski was running good 8100 at 11.7 afr. I adjusted the RRFPR to lean out a little bit at WOT (1/4 turn out) and afr went to 13.1. Turned RRFPR back in about 1/8 and back to 11.6-7. Rode for a while, no adjustments, back to 13.1. Gave more fuel and saw no change in AFR, gave more fuel and back to 11.5. Out of nowhere it went back to 13.1-2 at WOT so I gave about 1/3-1/2 turn more fuel and cruised back to ramp. Had to slow for a no wake zone and when I came out of ski was fine back at 11.5. No changed were made, machine didn't shut off or make any adjustments.

    Boost is at 10 psi. The O2 sensor in free air is reading 22.4.

    Currently at 70 psi on RRFPR and never had to be this high before for safe AFR.

    Weather was about 90* F with about 80% humidity.

    I called Riva and they said to check the "vacuum hose" for any blocks which there are none.

    Ski has run great for 2 years with this setup and this is the first time this or anything like this has happened.

    Thank you

    John


  2. #2
    imp0ster's Avatar
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    wow well you're killing your fuel pump for one. 11.5 is super rich for an X-SC especially at 8100. 70psi you're lucky you haven't completely blown your pump to pieces but I'm willing to bet it finally had enough and let go. Put your pressure back to 60 with the X-SC and get a new fuel pump.

  3. #3
    Lightning1's Avatar
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    I had this the other week, I solved my problem, but most people will have you test your heat exchanger for water leaking into your intake hoses.

  4. #4
    Lightning1's Avatar
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    I didn't see that, yeah, time for a walbro 255

  5. #5

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    If the pump is at 70 psi how can the pump be gone or on it's way out? This my old ski so I'm just curious as to the problem

  6. #6
    Moderator beerdart's Avatar
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    IMO there is nothing wrong with your pump I ran mine @ 82psi going on 6 years. I did have two walbros fail on a different boat.

  7. #7
    Your fuel pump will meet an early demise running those sorts of pressure.

    Your injectors are passing thru about 90% Duty Cycle or so and getting flaky. They all do this at about this DC. Then you are getting to 100% DC and the ECU is loosing all control of the AFR. Your injectors are about 40% too small. 60s would be a better bet., or even larger. All of this takes a tuner and data logger to sort out. No amount of messing with a regulator will fix this correctly.

    Andy

  8. #8
    Vern's Avatar
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    You can also get this due to very clogged filters on a stock pump in an older ski like yours. Either the filters are clogged, your stock pump is tired and starting to fail (first see at WOT where it needs full fuel flow/pressure), or your RRFPR is no longer functioning properly.

  9. #9
    Change the fuel pump, 99.9% of stock fuel pumps have a problem delivering the volume and high pressure consistently.
    Beerdart has unicorn stock fuel pump.

  10. #10
    imp0ster's Avatar
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    Beerdatrs fuel pump is made of golden rhino wang

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