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  1. #1

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    Oct 2020
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    2001 GTS RFI "limp mode"

    Hi Everyone. New to the forum and hoping you can help me go to the next step of troubleshooting. I had a 97 Speedster boat years ago. Carbs are easy. The RFI is causing me problems.

    2001 Seadoo GTX RFI - 2 stroke
    History: Bought used with new engine but not running right.
    Issue: RPM limits to 4400 rpm when warm (5-10min into run). Will run at 6840rpm with WOT as long as you stay there. Once you slow down the rpm limit starts.
    No diagnostic codes in CAN-DOO. No indicated codes in dash panel diagnostic (beeps and LEDs), No MAINT indicator.

    Usual first step is "change the rectifier". Yeah, I have read almost all the threads and here is what I have done thus far.

    Existing troubleshooting:
    new 4tec rectifier
    Stator wires all measure in spec
    Stator output voltage correct
    Ski puts out 13.8V to battery while running under WOT.
    Fuel pressure correct
    Fuel screens on pump have been cleaned
    new plugs
    Plug wires trimmed back at leads
    Front and rear fuse panels cleaned
    1A and 20A fuses intact
    TPS has been replaced (had dead spot in it)
    TPS properly zeroed out in CAN-DOO.
    Tried spare MPEM and had same issues.
    Swapped Bosch ECU within MPEM and had same issues.
    CHT sensor measures inspec.


    The limp mode supposedly will occur for low voltage to ECU. The only thing I have not done is measure voltage at ECU. I think this is Connector 3-P7 (red/purple) wire.

    Do the two power wires and ground wires to Connector 3 have crimp issues or other high resistance contacts that would cause a low voltage scenario?

    Any other suggestions?


    Thanks

    Jamie
    newbie in Austin, TX

  2. #2
    raiderteen's Avatar
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    When it starts limiting rpm like that after a bit of running feel the cylinders to see if one of them is colder than the other. Rave valves need inspected/cleaned and checked for function. Compression when hot needs checked. Ignition coil needs checked as well. It could be failing once warm/hot and dropping spark on one cylinder. This is where the cylinder temp comes in.

  3. #3

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    Oct 2020
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    Thanks. I did not check individual cylinders.

    The Rave valves have been removed, verified clean and verified vacuum actuation using a hand pump on the hose connection. The red adjuster caps are currently set flush.

    I did check that rave valves move freely when hot.

    I have not checked for cylinder spark when hot. I suppose a timing light flash looking for intermittent spark per cylinder can easily be done. I am not sure how I will tell the difference between coil limited rpm and ECU/MPEM limited rpm. The ECU is clearly driving the decision at 4400rpm. It is exactly 4400 rpm and runs completely normally up to that reduced performance limit.

  4. #4
    raiderteen's Avatar
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    The only spot in the manual I am seeing that mentions a MPEM commanded reduced rpm for the RFI models is "when battery voltage reaches 8.9 volts for at least 30 seconds, engine revolutions are limited to 4480 RPM" found on page 05-02-4 of the 2001 shop manual.

    Other than that limiter I do not believe the RFI MPEM has the ability to force a limp mode. Only the DI models mention anything about that in the manuals. So it has to be a electrical item malfunctioning when hot or a mechanical issue.

  5. #5

    Join Date
    Oct 2020
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    Thank you for the reply.

    Yes, I have read that line too. I wish it had more information related to low voltage at MPEM or ECU inside the MPEM. Would help my troubleshooting.

    It is not low voltage at the battery that is causing this. I forgot to mention the battery has been load tested and is kept on a charger along with a disconnect when not in use.

    I am pretty confident it is not a mechanical issue since the ski runs perfect as long as I don't drop below rpms after it is hot.


    I appreciate all the suggestions and leads.

  6. #6

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    Oct 2020
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    I just wanted to post a follow up to this issue.

    Turns out there was a bad CLT sensor. It would measure in spec all the way through warmup and then go open at full hot. This would shut down the ECU into limp mode. I built a pigtail to monitor resistance of the sensor while riding the ski. I thought it just went off scale and then noticed it was open.

    New sensor and sent my son out to test for an hour. Said it never ran better.

  7. #7
    Myself's Avatar
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    Thanks for posting the results.

  8. +1 by:


  9. #8

    Join Date
    Oct 2020
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    Well, Its spring and we have been using the craft. Ski was running well for many trips and just started doing the same limp mode. No errors on the dash. No codes in Candoo. Really frustrated I can't figure out what stops working when the engine gets to warm operating temp.

  10. #9
    Did you resolve this?


  11. #10
    What is a CLT Sensor? You mean a Temperature Sensor?

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