Seadoo GTX DI Missfire, Won't rev over 4800rpm.

[HarleyJace]

Hi there,

Just took my ski out on the water today and I'm having a few issues. I was out on the water for a good 5 minutes and all was running great, all of a sudden the ski sounded like it started getting a misfire and would no longer rev over 4800rpm. I rode it around for another 10 minutes hoping it would clear, it would then let me rev to 5000rpm but anymore then quarter throttle it would just start coughing and splattering. Im unsure if it matters at all but the battery had gone flat in it only after a week of not running, I charged it overnight but still didn't read as fully charged but fired the ski fine.

I have just put brand new plugs in it and I run ultimate premium fuel in it. A few guys at the lake mentioned that he may not be squirting out water but when you run the hose it's fine, they just said it could be setting itself into limp mode so it doesn't go and overheat, but engine temp seems fine, no warning buzzer and no maint. light or anything of the likes. Im unsure when the fuel filter was last replaced, could this be an issue giving the symptoms i've listed?



I'm not expecting a 100% answer but at least some guidance of what I should be looking at.

Thanks alot.

 

[SabrToothSqrl]

Rave valves or water regulator.
Or fuel filter

 

[seadoosnipe]

There are a couple things you need to check before you can do any real troubleshooting.

First, you said the battery went flat. The DI motor uses a good bit of electrical power. If your battery has a dead cell or two, then your not providing your electronics with enough power to run all your sensors and systems, regardless if your magneto system is sending power to the battery. With a loss of adequate electrical supply, your motor will have the systems you describe.

Second, you said the "tell tale" water line shows no flow of water while riding. If this is the case, then the ski could be overheating or dropping into limp mode. As for you saying there is water coming while on the water hose, that doesn't count. Why? Because the water being supplied for backflush from a water hose, has anywhere from 30 to 50 psi of pressure. With the water pressure, you are forcing water through your engine. When you are riding in the water, the jet pump supplies pressure to the cooling system. So, if your having a problem with your pump, your water supply line has build-up, or you've removed any of the cooling line calibrated fittings and replaced them with standard size elbows, or tubing, then your cooling system is no longer being regulated.

After you determine that your battery is supplying the motor with the proper voltage, and you know the pump is cooling the motor (it has water from your tell tale), then you can move onto troubleshooting.

There are only a couple things could make it backfire. A build-up of fuel because of weak spark (low voltage electrical system), then when enough build-up is present, premature explosion in the cylinder. Your fuel/air injectors and/or your fuel pump not working properly.

If you find the battery is holding a full charge, you find and fix the problem with your cooling system, .... if you still have a problem, you'll need to have a shop manual so you can do the tests on your air compressor, fuel and air injectors, fuel pump and air solenoid. The DI motor is a really hard to troubleshoot motor, unless you have a mechanic actually helping you to do a process of elemination, so you can move on to the next step.

Personally, I don't think I would ever own one because of the high pressure injection system. The RFI (rotax fuel injection) motors don't use the air compressor (which is needed to overcome cylinder compression). They inject fuel on the low pressure side of the cylinder and casing.

Good luck, first things first, get a new battery, make sure your cooling system is working properly in the water, then go from there. Cheers!

 

[HarleyJace]

Thanks alot for your help, that at least gives me somewhere to start and now start eliminating some issues.

I put a multimeter on the battery and when shut it off it's reading 12.3 volts, when you put the key in, drops to 12.1 and when you start it on idle it sits on 12.7 and will only go upto 12.9 when you rev it, so there could be an issue there.

 

[SabrToothSqrl]

voltage

that's close but I don't think the full power level it should be.

But like I said, I would also check the RAVEs and the water regulator. both of these systems control the engine's ability to hit 7k wide open.

There is an article on here about how to clean your RAVEs, I will see if i can find it.

here:
http://www.seadooforum.com/showthread.php?37588-How-to-service-Rave-Valve-Pictorial&highlight=RAVE

start at "Now take a #5 hex to take the 2 screws out"

you want to remove the ASSEMBLY from the hull/engine, THEN take it apart. prevents you from dropping small pieces in the hull and spending 2 hours looking for them.

Else the write up is fine, your RAVEs will look a bit different, but same idea.

Clean these, then get back to us.
Also, from now on, clean them every fall.

 

[ski-d00]

voltage regulator is a very common failure on the di and sounds like your problem.

 

[HarleyJace]

Okay, thought I would reply for those who are interested.

When I purchased the ski, the seller said the ski just had a fresh rebuild and supplied a receipt, he said it had done 11 hours and he had just done the 10 hour service. Fair enough I thought. I took it to a seadoo mechanic to get the issue I'm having diagnosed. Plugged the diagnostics in and mention it's only just done 10 hours now according the computer since the rebuild, and I've done 8 of those. No codes come up, he fired up the ski and instantly mention it had a pretty solid knock/tapping noise. He pulled the raves out to find they heavily damaged from the pistons hitting them. He mentioned it would've had oversized pistons put in on the rebuild but they didn't machine the raves to accommodate for the larger pistons. It's damaged both the raves and the pistons pretty heavily and the original place who built the jet ski is now saying it's not there issue etc.

Thanks for your help guys.

 

[Seadoobuddy]

If you have the receipt, then you have some leverage. I assume you took it to a different mechanic other than the one who did the rebuild/bore.

I would say that it is their issue. They didn't do it right by shaving the raves.

If possible take the old owner with you to see the guy who rebuilt it. Saying you have proof that it was not done correctly. Talk to him like a professional, no swearing, yelling,etc. Maybe he'll do for parts, no labor or other agreement between the 2 of you.

Next step could be small claims court if you have that in your county. Over here it's for claims under $2500, no lawyers allowed. You each state your case and the judge decides.
Good Luck