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  1. #1
    GPRXP vspec1's Avatar
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    fuel pump/out of injector

    I have a 2005 RXP with the following mods, X-charger w/wheel and spacer, riva ecu & 50lb injectors, rude fuel controller, 15-20r prop, riva intake grate, 4" intake, thru hull exhaust, x-intercooler, valve springs and retainers.

    Everything was perfect last week until I decided to add the wheel and spacer to the charger. Testing at the lake a/f was in the 12.5 to 12.7 @wot. No matter how much fuel we thru in up top, a/f stayed the same. Before the spacer and wheel a/f was a steady 12.1 to 12.2

    I have a rude fuel pressure reg. but it was at the house. When I got home I put it on and set base pressure at 60, no vacuum line attached. When I rap the throttle, no boost, fuel pressure drops. Do I need to upgrade to the walbro pump? I do have a set of 60lb injectors but that would mean I would have to re-tune the ski. Looking for the simple solution right now. I think its a fuel delivery problem? I don't think I am maxing out the 50lb injectors?

    Oh, last week the ski ran 79.5 in the florida 90 degree heat, before the wheel and spacer.


  2. #2
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    The most important thing with your fuel pressure is... where is it at WOT It should be at least 5-6 psi above your base pressure. With your mods and the issues many have had with the oem fuel pump... I would not think twice about replacing it. There only $90 bucks or so, and a direct easy replacement!

  3. #3
    speedskixp's Avatar
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    It sounds like your injectors are running close to 100% duty cycle wich is why the fuel controller is not helping. You can either add some fuel pressure or step up the injector size and tune the controller accordingly. I also suggest getting the fuel pump.

  4. #4
    GPRXP vspec1's Avatar
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    Thanks guys, Thats what I was afraid of, I guess Its no big deal. I will pick up a walbro pump tomorrow, and throw in the 60's. Is the walbro a gss342? Thanks, Patrick

  5. #5
    speedskixp's Avatar
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    Quote Originally Posted by vspec1 View Post
    Thanks guys, Thats what I was afraid of, I guess Its no big deal. I will pick up a walbro pump tomorrow, and throw in the 60's. Is the walbro a gss342? Thanks, Patrick
    Yes, gss342.

  6. #6
    Having Fun jp1300r's Avatar
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    Patrick, Did you get the prop repitched before trying to tune in the new SCer? I was at 8550rpm last weekend on your ski. You should be on the limiter, if you didn't get the prop done. That will mess up the AFR.

  7. #7
    speedskixp's Avatar
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    Quote Originally Posted by jp1300r View Post
    Patrick, Did you get the prop repitched before trying to tune in the new SCer? I was at 8550rpm last weekend on your ski. You should be on the limiter, if you didn't get the prop done. That will mess up the AFR.
    +1. If your on the limiter it will be lean.

  8. #8
    GPRXP vspec1's Avatar
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    Hello JP, I was on the limiter, then we put cals 81mm nozzle on to bring the rpms down to 8500-8550. I just dropped the prop off to Duke so he can do his magic....My main concern is the lack of fuel pressure when I just rap the throttle on the hose. It drops like 5-6 pounds with no load. Whats it doing on the big end? I'm going to put a Walbro pump in it Monday and re-test. I'll keep you posted...I'm sure you My ski will take you 80+ on Sun

  9. #9
    Having Fun jp1300r's Avatar
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    I hope the fuel pump works for you. Get the prop pitched for the 83mm nozzle. It may take two tries to get it just right. I think Hector needs a fuel pump, too. That ski is going to be flying by next weekend. Close to 82mph I am guessing.

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