Seadoo XP Limited Only fires on one cylinder

irish199

New Member
Have the strangest issue with my 1999 Seadoo XP Limited and can't work it out. Seadoo will only fire the first time if one plug is removed. It will not start with two plugs in. Once it has started the first time, I can then run it with both plugs. Can start and stop it consecutively, but if left more 10 - 15 minutes I have to repeat the process.

Once running, it will idle on one cylinder and when I rev, it will run on both. Have tested by pulling the spark plug leads to confirm. Have tested spark and it seems to be fine.

I've replaced battery, new spark plugs, have tested resistance on stator and confirmed no short. I have also done a compression test and confirmed all ok (150 and 160). Only thing I have not done is replace the trigger coil simply due to not being able to find a replacement in New Zealand.

Any advice would be greatly appreciated.
 
Yes seen the trigger coil. No metal shavings on the trigger coil but was a tiny bit of corrosion on the metal sensor. Cleaned it up and put it back in but have the same issues.
 

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I am not very familiar with your ski but doesn't it have a voltage regulator? I would check that out and see if it is functioning.
 
I wasn't aware it had a rectifier. Couldn't find one on the parts catalogs.
I'm not 100% sure it has one, if it does it might also be incorporated in the MPEM, like mine is (98 GTX Limited w/951). Which means its not easy to repair. Look in your shop manual, go to charging system and look for rectifier/regulator (its one unit), mine says it transforms A/C voltage to DC and the regulator keeps voltage at a steady level 14.5 to 14.8, this is for the 98 XP limited too.
 
It won’t have anything to do with your stator or trigger coil or regulator, your engine fires both cylinders at the same time because there is only one trigger coil, so if you have spark on both cylinders it should run on both, if not you likely have a issue in the carb of the cylinder that isn’t running or you could have a leak in the bottom end, if you could spray some fuel in the carb that isn’t working when it is running and it starts to run on that cylinder you’ve narrowed the issue down, you would need to pull the carb apart and clean and check it and make sure it’s set to spec. If that doesn’t fix it you need to do leak down test on the engine.
The regulator is in the mpem on those units
 
It won’t have anything to do with your stator or trigger coil or regulator, your engine fires both cylinders at the same time because there is only one trigger coil, so if you have spark on both cylinders it should run on both, if not you likely have a issue in the carb of the cylinder that isn’t running or you could have a leak in the bottom end, if you could spray some fuel in the carb that isn’t working when it is running and it starts to run on that cylinder you’ve narrowed the issue down, you would need to pull the carb apart and clean and check it and make sure it’s set to spec. If that doesn’t fix it you need to do leak down test on the engine.
The regulator is in the mpem on those units
The 99+ 951 engines are twin coil and not a wasted spark like the 787 and smaller engines.
 
Yes the 951is a twin coil, I’m not so sure about it not being a wasted spark though…I’ve never tried to to see, but it only has one pick up coil and the flywheel only has two protrusions so how would it know whether it was on cylinder 1 or 2 to fire.
The only point I was trying to make was if it’s running on one cylinder it won’t be the stator or pickup coil or the regulator.
The first thing that needs to be figured out is if it isn’t running because it isn’t getting a strong enough spark? You could switch the ignition coils to see if the problem switches sides.
Or if it isn’t getting the right fuel mixture? Is it too rich (needle and seat leaking)?
When trying to start it with both plugs in is the one that won’t fire wet? If it is your carb is likely flooding the cylinder.
If it’s dry try dropping a little bit of fuel down the spark plug hole and see if it will fire on that cylinder. If you have compression and fuel and spark it should run.
 
Yes the 951is a twin coil, I’m not so sure about it not being a wasted spark though…I’ve never tried to to see, but it only has one pick up coil and the flywheel only has two protrusions so how would it know whether it was on cylinder 1 or 2 to fire.

The magneto has 3 or 4 protrusions on the twin coil setup. One long and 2 or 3 short, cant remember.
 
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