SeaDoo GTX DI Issue Not Idling on PTO Cylinder
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  1. #1
    PWCToday Newbie
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    Sep 2019
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    Houston, TX
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    SeaDoo GTX DI Issue Not Idling on PTO Cylinder

    I am in desperate need of help troubleshooting my 2000 GTX DI. The engine blew with ~220 hrs on it, a hole in the piston by the rave valve. Pulled it, sent to SES for a rebuild. Had all fuel and air injectors cleaned/serviced. Reinstalled, went through everything. Fired up for break in and had some voltage issues. Replaced rectifier with a used OEM off e-bay (OSD was backordered). Break in went pretty well, had an occassional misfire under load but the ski had been doing that for years. Finally after 5 hrs or so went WOT briefly for the first time. Sounded great but as soon as I throttled down the engine started running really rough. Ever since, the idle is rough and low end power is lacking. It starts to smooth out at higher RPM but I am afraid to push it too hard. The engine will not idle on the PTO cylinder alone. MAG alone starts/idles smoothly.

    Troubleshooting:
    Compression on both cylinders is exactly 120, verified with multiple gauges.

    Have swapped spark plugs, air injector, fuel injector, coil, and spark plug wires from one side to another. No change.

    Fuel pressure is uneven at low RPM's. This is caused by my air pump, but it smooths out with any RPM increase. See video:

    Air pump puts out ~110 psi dead head. To test if this was the problem, I supplied air to the fuel rail with a tire inflator and it regulates smoothly to 80 psi. I then ran the engine using air supplied from the tire inflator and it sounded the same, no change in PTO idle ability.

    Fuel pump dead head pressure exceeds 110 psi.

    Battery tested 100% charged and good by 2 different parts stores.

    PTO reed has been removed twice for inspection and looks great.

    I mistakenly identified the fuel pump as bad (in reality a bad gauge) and bought a used OEM replacement from WestSidePowerSports. No change.

    The followign faults have appeared 1 time over the course of recent troubleshooting, and some were when the battery was low:
    PTO TPS out of range
    Wrong pattern sensed on encoder
    Intake pressure sensor out of range

    A MAG TPS out of range code has appeared multiple times but is not repeatable. I unpluged one TPS at a time and the engine ran but still would not idle on PTO only.

    If you run the engine at a higher RPM, a deactivation of the MAG cylinder in CanDoo will NOT kill the engine. But every time you cut the MAG at idle, it dies.

    CanDoo activation of the air and fuel injectors sounds good. CanDoo coil activation on both cylinders produces a nice spark. A check of PTO spark while cranking shows a nice spark. Fuel is definitely getting into the PTO cylinder.

    What else can it be? Something electrical/MPEM related? Something mechanical in the engine that does not impact compression? This ski is in amazing condition otherwise so I really want to figure out the issue.

  2. #2
    Resident Guru
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    Re: SeaDoo GTX DI Issue Not Idling on PTO Cylinder

    First, the air pressure cannot vary like that, fuel pressure will follow-suit. Have you replaced the compressor reed valve? In what condition is the compressor main hose, the small plastic tube to the rave solenoid valve, the solenoid valve itself? Is there a bad, incorrect or missing o-ring in the air-side of the fuel rail?

  3. #3
    PWCToday Newbie
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    Re: SeaDoo GTX DI Issue Not Idling on PTO Cylinder

    Quote Originally Posted by rdjeep View Post
    First, the air pressure cannot vary like that, fuel pressure will follow-suit. Have you replaced the compressor reed valve? In what condition is the compressor main hose, the small plastic tube to the rave solenoid valve, the solenoid valve itself? Is there a bad, incorrect or missing o-ring in the air-side of the fuel rail?
    Compressor reed has not been replaced. I thought that was a likely culprit which is why I bypassed it and ran the engine off a tire inflator instead. The compressor main hose is new as I had to hack the original to help with troubleshooting. Small tube to the solenoid looks fine, as does the valve. Pretty sure the fuel rail is good as it regulates pressure to 80 psi and holds a bit lower after the motor stops cranking.

    Thinking back to when I was providing the engine air from the tire inflator, not supplying the rave solenoid should not affect idle performance, should it?

  4. #4
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    Re: SeaDoo GTX DI Issue Not Idling on PTO Cylinder

    I have run my fuel rail from my shop air compressor as a troubleshooting exercise also. The tank of the air compressor yields a much more stable air flow. A tire inflator may not be the best as an air source for this.

    The solenoid will be closed at idle anyway, so no improper affect. I think it opens by software command around 6000.

    Now, when you say certain things "looked good", does this mean just a visual inspection, or did you test with soapy water looking for tell-tale bubbles? The air compressors can overheat and melt the small plastic line to the solenoid. Bad diaphragms in the regulators can also be sources of leaks, too.

  5. #5
    PWCToday Newbie
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    Re: SeaDoo GTX DI Issue Not Idling on PTO Cylinder

    Quote Originally Posted by rdjeep View Post
    I have run my fuel rail from my shop air compressor as a troubleshooting exercise also. The tank of the air compressor yields a much more stable air flow. A tire inflator may not be the best as an air source for this.

    The solenoid will be closed at idle anyway, so no improper affect. I think it opens by software command around 6000.

    Now, when you say certain things "looked good", does this mean just a visual inspection, or did you test with soapy water looking for tell-tale bubbles? The air compressors can overheat and melt the small plastic line to the solenoid. Bad diaphragms in the regulators can also be sources of leaks, too.
    Understand the tire inflator may not be an ideal source of air. Given the air pressure fluctuations, suppose I am best to continue troubleshooting that system, either the compressor reeds or the air pressure regulator. The rave valve and line was just visually inspected. I think it held pressure when I checked dead head pressure but perhaps I should try that again. It will be a while before I can get into it again, but I am determined to fix it!

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