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  1. #1

    Join Date
    Sep 2020

    2015 VX Deluxe Second Engine Failure

    I have a 2015 Yamaha VX Deluxe. Original engine failed due to cylinder number 4 piston having a catastrophic failure while riding. Decided to replace with new SBT engine (not rebuilt original). New SBT engine ran great for around 4 hours and same failure happened. Still under warranty so sent back to SBT. The failure analysis from SBT indicated that cylinder number 4 hydro (fuel) locked due to not firing and large amount of fuel dumping caused the piston failure. I have had the fuel injectors tested and cleaned and no issues. I also had the ecu tested (carmo) and they could not reproduce any issues with the fuel or ignition. I checked each ignition coil per the service manual and all were within spec. I have the replacement SBT engine in the ski and everything is running great again. No codes using Cando software. I am nervous about the same thing happening again since I have not been able to find the root cause. Even though the ecu has been tested, I am debating purchasing a new one but hate to just throw parts at it. Any experience with this issue or suggestions would be appreciated.

    pics of original engine failure
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    Last edited by JMann; 08-01-2021 at 03:16 PM.

  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Which engine is in this model?

    Perhaps replacing the front fuel injector with an OEM new injector would eliminate the possibility that the original fuel injector was/is sometimes sticking open.

  3. #3

    Join Date
    Sep 2020

  4. #4

    Join Date
    Sep 2020
    I did send the injectors off for testing and they found no issues. Also, as the engine was disassembled from the first failure, the injectors and ignition coils were pulled and were not kept in the same order. I guess there would be 25% chance I put the same injector back in the same cylinder. I assume the testing would have identified any issues, that’s why I am thinking ecm/ecu since I read the open injector issue was happening on older MR1 engines due to an ecm/ecu issue.

  5. #5
    This is how I run a jetski shop in the desert nmpeter's Avatar
    Join Date
    May 2008
    Elephant Butte New Mexico
    considering the labor involved in getting an engine back to SBT for a "free" replacement. I'd replace the injector on the suspect cylinder with a brandy new one, but seeing that the parts were mixed up(!) you should bit the bullet and replace all the injectors. While SBT's warranty is really good, repeated failures of the same type are going to cause some difficulty. A stuck injector is fairly hard to ignore, bad fuel smell on the dipstick and a significant power reduction

  6. #6

    Join Date
    Apr 2007
    I would also check the pins in the deutsch connector for the coil on that cylinder. Could be broken in the connector and the plug not firing but still dumping fuel in the cylinder.

  7. #7

    Join Date
    Sep 2020
    Thanks for the responses. I will check all the connections. I have fired it up on the hose and it is running great much like the last engine did before the failure. Maybe riding the ski and hitting waves is causing something with the wiring at higher rpm. I am going to keep checking. I wish I could get it to reproduce the issue so I could diagnose and repair. Ran great last time during break in period and up to around 4 hours before the catastrophic piston failure. I sure hate to throw parts at it (injectors/ecu) if I can’t fine the root cause.

  8. #8
    i bet itís your ecu

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