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  1. #1

    2001 GTX RFI mysterious injector issue:

    I think i got a good one for y'all to puzzle over: (my first and only other post was a year ago when i sunk the bike and flooded the engine when towing without closing off water intake lines, i have learned a lot since then)

    here we go:

    the GTX (the dragon) has run for me for a year, (with numerous various minor issues, but nothing thats kept her down, especially engine wise. engine has been solid). The starter was going (and i new it) and it finally went (just got kind of a weak grinding sound out of it in the end). So i bought a new one and dropped it in. no major problems besides that the starters are under the engine (old starter was definitely spent, barely a kick and slow weak spin when hooked to car battery). after the reinstall:

    fired right up on the trailer, sounded fine. put in water ready to go, and then new problem: would crank but not start. could start if lucky but no horses, throttle wide open got it to 2500/3000rpm but thats it, subplaning.

    only running on 1 cylinder. (the front cylinder) (this is confirmed, i know for one reason because i can pull the plug coil off the back cylinder when its running and it still goes, cannot make it work with the front plug disconnected, even when pulling front plug at high rpm)

    i confirmed both plugs are sparking solid.

    i looked at fuel:

    pulled the fuel rail and this is what i found:

    crank the bike with fuel rail out and front injector spits fine, nothing from back (including no clicking feeling from the injector itself).

    check injectors: switched injectors (front to back, back to front) and found the front injector (formerly the back one with no action) working fine, nothing from the one in the back spot.
    so both injectors are good.

    so its the fuel rail or the wiring harness/connection (RIGHT??)

    check the fuel rail: switch injector wiring (front to back, back to front): back injector spitting fine, nothing on front. fuel rail good.

    bad connection! replace wiring harness (with identical from other bike) and hook up. ........ SAME PROBLEM!


    switch mpen or whatever that big electronics box in front is, reprogram key / bike to start ...... SAME PROBLEM.

    ummm what????

    so thats where im at. here are some other things i have tried:

    it seems there is no power going to back injector. using a test light it seemed that there was no working ground for the back injector. i added a ground to the block. this brought the injector power, HOWEVER: the injector was not spitting like it should, it simply opened and stayed open, spraying like a fire hose. (flooded engine with literally more than 1/2 gallon of fuel discovering that one). next, i tried wiring the grounds from the 2 injector wire groups together: now both opened and stayed open. finally i simply wired the back injector directly to front (piggy-backed them): they both spit properly now, however they are syncronized instead of alternating like they should. rigged like this the bike will run again, it will start and idle strong in the water like it should, however there is no low rpm power. i cannot slowly accelerate or easy it onto a plane, it will stall. if i go from idle to WOT it will almost stall, then overcome and blast off hard (like it should) it runs at 90% top end of what it used to (about 6750-6800rpm, it used to do 6950-7100). from high RPM i can ease it down to about 4500/5000rpm without issue, but it wants to stall out if running any lower than that.

    although i messed with RAVES to try and re-tune it to work better with the injectors wired up like this, thats not happening and i would like to fix it properly anyway.

    so what is the deal: back injector not spitting: its not the injector, its not the wiring (assuming the new wiring harness doesnt have the same problem as my original might) its not the computer. is there a random sensor or something that might have gone bad and is not allowing the computer to send the power to the back injector? and why might this have happened after changing the starter (when this was not an issue before) (and i am pretty sure i didnt break anything or forget anything when putting it back together after the starter change)

    so hows that, for your consideration...

    thank you

  2. #2
    come on, no one has a clue or what? me neither.

  3. #3
    Cliff's Avatar
    Join Date
    Jan 2006
    Middle Tennessee
    I am pretty sure that engine starts and idles on the front cylinder only. That is why you have no fuel at crank. Try opening the throttle about half way and see what you get.

  4. #4
    Quote Originally Posted by Cliff View Post
    I am pretty sure that engine starts and idles on the front cylinder only. That is why you have no fuel at crank. Try opening the throttle about half way and see what you get.
    ya i believe you are right about that. it wont run on the back cylinder alone even after reved high. the computer is failing to tell the back injector to fire for some reason.

    i got a possible long shot theory from a guy the other day who suggested that metal shavings inside the engine/flywheel case might be causing a short somehow and interfering with a sensor or the computer somehow. that seems a little far fetched to me, but i am pretty sure there are plenty of filings floating around in there, its an older bike that had been running a while on a questionable starter, plus when i pulled the old starter i could see wear on the teeth etc.

    not committed to ripping it all apart again just yet, but will soon anyway.

    any other ideas? i am really hoping for a "its because (x sensor/wire/fuse) is bad) come on people. someone knows the magic easy answer here. PLEEEEASE!

  5. #5
    SELF27's Avatar
    Join Date
    May 2013
    Austin, TX
    I have one of these boat in my shop right now with same issue. customer brought in and said sat all winter and ran fine before that. took to another shop and they replace starter motor and still could not figure out what was problem. I also thought it was injector failure until testing voltage and swapping like you did. I found out that issue was encoder wheel had one bent tooth and one broken tooth. looks like something from old starter abbendix came off and damaged encoder wheel. did not have old starter to verify. encoder wheel very expensive from seadoo. can remove crank position sensor and inspect through hole in front cover.

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