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  1. #1

    05' Seadoo 3D 787rfi new engine Won't start

    Just rebuilt engine, the engine ran perfect for 12hours 10 of which i followed break in procedure never going full throttle but constantly adjusting throttle. after about the 13th hour the ski will not start anymore. It turns over completely fine and sounds normal. I checked compression in both pistons which was about 155 in both. Mechanically it sounds great, not like there is internal damage, it sometimes backfires if I continue to hold the throttle and starter button down. If it is timing why would it work for the first 12 hours? It has a new rectifier, with 13hrs of use, new plugs gapped to .02 (new as in after it stopped working), before the 13 hours I checked fuel pump and injectors and they were in perfect working order, I wouldn't expect them to just go bad, but could check again. ecm problems? maybe bad rectifier, is there a way to check this? any help would be much appreciated to helping me get this running again, if I think of anything else I will update.


  2. #2
    anything? .... no help, mpem?

  3. #3
    roundtopjeff's Avatar
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    The first thing I would check is the fuel pump. I know you said you checked it 12 hrs ago, but the same thing happened to me and it was the pump. They can just quit overnight.

  4. #4
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    I'd be giving the rv valve the stink eye as well as the pump..was it a full rebuild or only top end?

  5. #5
    Ok thanks for input, I'll try and check the pump by this weekend.

    Nmpeter - Yes it was a full rebuild, new crank, rods, bearings, pistons, I calibrated the RV myself and was quite meticulous with it, if the pump checks out good though that'll be the next thing i'll check, thanks for input.

  6. #6
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    the rfi has lots of bits that could be checked with a ohm meter.

    one thing to check would be that the cps is ok. real easy..on the front of the stator cover.

    that provides a start signal for the fuel pump ( and shuts it off if the engine stops turning)

    fairly common failure items as far as fi systems go.

    I hate dealing with fuel under pressure.....

  7. #7
    I checked the pump, and cps both checked out good unfortunately. I took the ski to dealership to have them pull codes, they got back to me and said it was a bad ecu, and wanted 1300 to fix it. For diagnosing it they want 300 to pick up the ski. He also said he swapped out parts to make sure it was just the ecu. That seems like a ridiculous price just for diagnosing a problem/ pulling a code even if he did swap any parts?

    I'll try and go talk to them tomorrow and ask them what they did that justifies 300 dollars, if they swapped out the ecu couldn't I just buy one and swap it out myself or does it need special brp/dess/mpem coding yata yata yata b.u.d.s. to properly work?

  8. #8
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    ripoff, what is the labor rate there $ 300 an hour?. A new mpem is pretty expensive bit however.....

    you would need to code a key for a new mpem


    sounds like a penalty price to me. Did you go in there spouting off about all the great stuff you did?

    you'd pay less than half of that for a diagnosis at my place, unless you wasted a lot of my time during the intake arguing about what I should be looking at.

    i.m not real tolerant of time wasting. If you are paying for it different story.

    I often turn away work from guys who tell me stuff like

    I just rebuilt my carbs, all you need to 'do is adjust them so it runs good. Shoudn't take you more then ten minutes


    yeah..2 minutes to tell you I need 2 hours minimum to go thru your stuff before I even put it in the tank.

    pay em an hour of shop time..more than that you shoud complain direct to seadoo, unless you made the mistake of signing a blank work order

  9. #9
    No I did not go in there fibbing about anything, just said I came in to get ski looked at, it doesn't start up. Service guy came out and asked me what happened, I said it has a new engine and ran great for 12hrs then on the water just decided to die and would not start back up, if I had to guess I think its an electrical issue. that's literally all i said. Never mentioned anything I did myself, he was kind and said verbatim, "i'll bet you i can figure this out." little cocky, that's fine, its his job and that's why I brought it in, last resort though I had a good idea it was the mpem.

    He ran diagnosis on lots of different parts, TPS, fuel, the only code he got when plugged in was P0231 which reads 'fuel pump shorted to ground or open circuit', he tested fuel pressure and injectors, APS was all over the place he said, replaced it with a known working APS and got same malfunctioning result. verified ECM to APS continuity - all good. checked rotary valve timing, crank twist, compression yata yata yata its a long list, most stuff I already knew, he said he was 95% sure its a bad ECU, he would have swapped it out but didn't have one in shop. the other 5% he says could be due to a sheared woodruff key on the magneto side. He doubts it is for I forget his reasoning but sure.

    Anyways yeah we did sign a blank work order, i disagreed with the price, very unethical IMO, 100 an hour, for 3hrs of diagnosing, I got no deal, no discount, just a nice ass reaming. I'll know for next time to make sure to have a set amount I agree to before they begin anything.

    Anyways, I'm done working on this ski, going to sell as-is, posted on ebay
    Thanks for all the input nmpeter and roundtopjeff, much appreciated.

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