1995 XP 800 Intermittent Stall Issue

[evanssd1]

I have been having some really weird issues w/ my 95 XP 800.

Symptoms:

At any given speed (even happened while warming up engine on trailer) my ski will suddenly drop down to idle speed and the throttle will be completely unresponsive. If you switch the ski off and on with WOT it runs correctly again. This occurs at what seems to be completely random intervals.

I have studied other forum posts and the factory manual. It seems like w/ these models the ignition is ran directly off battery power which would rule out the stator and/or the rectifier. I ran a power test on the battery and everything was in the correct range while on the trailer, although I couldn't re-create the problem. I am very curious what the numbers would be when the failure occurs.

I have a new coil on the way but when looking at the old coil last night it appears to have been replaced once before by a previous owner. The unit is a DENSO Marine 278000383 129700-3281. Anyone know if this is OEM or a replacement part?

Anyway, after reviewing everything, I am starting to think I have a failing MPEM. What else could it be? What else could drop the RPMs down to idle levels? I have a tiny tach on the way and I will do some more testing this weekend with the new coil. In the meantime, does anyone have any ideas?

I have thrown way to much money at this boat already but just can't let it go. MPEM replacement sounds very expensive!

Thanks in advance!

Sean

 

[Dr Honda]

You have me stumped on this one. Yes, the ignition on the 800 is a DC (battery voltage) ignition. but, the ignition alone shouldn't be able to bring the engine to an idle, if you are holding the throttle open.

Personally, I would not be pointing my finger at the MPEM.

Go you still have the gray fuel lines?

 

[evanssd1]

all grey lines have been previously replaced

carbs were rebuilt by a shop

i should also say that the top end of the ski is only 46 (so something is amiss)

i am just at a loss on what to look at / replace

rectifier showed 13.6 @ some high rev (no tach on this one) tiny tach in the mail

when the ski goes to idle it happens instantly, like 35MPH to BAM idle, so suddenly it throws you forward.

 

[6KJR]

You guys sure that the coils on the machine run off the battery? My stator was bad on my 97 Spx (and maybe their different from yours) but it would loose my spark out of no where until it cooled down again. Battery was fine. No spark.
Either way it's an odd problem you have there. Hopefully it's not mpem. Have you checked the stator out?

 

[evanssd1]

I am going to inspect the stator sometime this winter, that type of maintenance will take me some time to complete (and i have kids competing for my time) :nopity:

looks like we will have one more nice weekend here in Tennessee so i am going to hook up my new tiny tach, volt meter, and a new coil and go on some test runs. hoping to get some more diagnostic info...

 

[Dr Honda]

You guys sure that the coils on the machine run off the battery? My stator was bad on my 97 Spx (and maybe their different from yours) but it would loose my spark out of no where until it cooled down again. Battery was fine. No spark.
Either way it's an odd problem you have there. Hopefully it's not mpem. Have you checked the stator out?

Yes... the 800 has a DC-CDI system. 720's and smaller use a "High Voltage" MAG system. Just because your battery is good, doesn't mean that the system will still work if you have other issues. (like a bad stator) it still relies on clean voltage, and a good solid pulse from the pickup coil.

BUT... you were loosing a spark... this problem is it's going back to an idle.


If the engine is actually going to an "Idle", and not just trying to die... it would have to be fuel related. I don't' think the CDI can pull enough timing out of the system to actually drop the RPM's back to 1500 with the throttle open.


BUT... check the pulse coil. They are known to break away from their mounts, and just before they snap off compleatly... they do weird things.

 

[evanssd1]

"if the engine is actually going to an "Idle", and not just trying to die"

First off, thanks for your replies!

I am not sure if I would know the difference between going to idle versus trying to die. Maybe testing this weekend with a tach will help me identify this? I can just tell that the ski will go from 35MPH (or any other random speed) instantly down to put-put-put-put mode and moving the throttle does nothing. On/Off switch WOT works every time to get it back moving.

Also my max speed is 46MPH which is low for this engine, not sure if I have two problems or they are related to the same failing component. Again, I have no idea what RPM I am running at that speed. Can't believe a tach wasn't standard on these things

I also am not familiar with the pulse coil, I need to figure out what that is and how hard it is to inspect.

 

[Dr Honda]

I am not sure if I would know the difference between going to idle versus trying to die.

Welllllllll..................


You have to know. Since we aren't there, you have to know enough to give us good info.

Since you made reference to "Put-put-put"... is it a smooth idle, or is it a stumbling, rough, low RPM thing??? If you say idle, in my head it's running clean and smooth at a low RPM.

I also am not familiar with the pulse coil, I need to figure out what that is and how hard it is to inspect.

If it's a rough stumbling thing... then I would probably blame the pick up coil. It's behind the stator cover.

 

[evanssd1]

:blush:

i will pay better attention this time, and i will note what the tach is saying at high end speed and at the point of failure, that's the only way i will know i guess. even normal idle seems sketchy to me, it definitely not smooth.

 

[Dr Honda]

I'm not trying to be harsh... I just don't want to spend time chasing the wrong thing. :cheers:


BUT... just to be clear... a 2-stroke won't be as smooth as your car engine...but it should be relatively smooth, ans stable at idle. If there is a lot of vibration, or it seems to fire uneven, that is not normal.

Take your test ride, and let us know what you figure out. (be extra observant)

 

[evanssd1]

sorry, i just never had a tach until now, the engine does vibrate while running, i can take a video this weekend and post a link, i wasn't sure it it was just out of balance a little or if it was normal or what!