717 - Demonic Possession - Self Starting

[Ernest Jones]

Hey guys,

On a neighbors '95 XP w/717 we are experiencing demonic possession. The unit self-starts, for unknown reasons, every once in a while, even with the lanyard removed. We have just installed a new starter solenoid as the old one packed it in. We used an OE solenoid.

I figured, after that, there would be no issue with this self-starting thing. Today, while under cover, it just self-started, even though the carbs are off! I guess there's enough fuel vapor in that hull....

What the heck could that be?

 

[Grim]

i would test your start switch, makes sure it isn't shorting somewhere. Where is the key when this happens?

 

[Ernest Jones]

Key is out of it so it should not crank or start no matter what. The lanyard and solenoid were tested for functionality before and after replacing the solenoid. I'll have to look at the wiring diagram I guess to see what can trigger the solenoid.

 

[Ernest Jones]

It looks like the only thing that could cause this when the lanyard is removed is something occurring in the 'MPEM'.
Looking at the wiring diagram, the solenoid is activated by the MPEM assuming the lanyard is closed and the start switch is pressed. Given that the lanyard was removed my guess is the MPEM is somehow activating the circuit.

 

[burtshaver2021]

If it continues to run without a carb or fuel you better call a priest

 

[Ernest Jones]

If it continues to run without a carb or fuel you better call a priest

I am not kidding, it ran for a few seconds sans carburetors. It even spat water out the back! I had to run over, pull the cover and disconnect the negative cable. But... there would be fuel puddled up down there from neighbors numerous attempts to start and also the front carb was dumping fuel in at idle. Engine compartment itself stinks like gas! Not a word of a lie, it actually ran....

Just to close off the diagnosis, the safety switch where the lanyard goes is normally open. So, to close the circuit it you have to have the lanyard installed. Both wires for that circuit go straight back to the 'MPEM' normally I'd call it an ignition box.

The start/stop switch is normally open. It closes when you press on it. One wire from this is ground (BK) and the other is Yellow w/red Ground is found somewhere on the 'frame' and the YL-RE goes straight back to the 'MPEM'

My assumption of the logic on the 'MPEM' would be, in order for the starter to be allowed to operate, the MPEM would need to see safety switch circuit closed (continuity) indicating lanyard installed. In order for the starter to actually operate it would need to also see the start/stop switch grounded (activated).

Assuming both are true the 'MPEM' would then activate the starter solenoid through the BK & YL-RE lines.

Since the lanyard was not installed it would not matter if the starter switch was pressed (this was tested before and after solenoid was installed). The starter should not be allowed to operate because the circuit is open. Same with the start/stop button, it's also open. The only way the solenoid can be activated is if the 'MPEM' does it. Therefore, it's got to be the MPEM itself. As far as I can see, anyway.

 

[burtshaver2021]

That makes sense about the fuel sitting in the crankcase, it sounds like you have a better understanding of the wiring than I do. The only things I could say that might help is, does it look like anyone had tampered with the lanyard switch,, i can’t recall exactly but I thought I seen some of the aftermarket ones were backwards or something ( I really have no clue ) and is the MPEM OEM? Again aftermarket rarely seems to work correctly. Best of luck, make sure that machine is tucked safely on a trailer with the plugs and battery out of it so it doesn’t get away on you

 

[Ernest Jones]

I think your assessment is basically spot-on. When he got it the other day it came with a new lanyard switch (not installed) so I did that for him. It hard 4 terminals but only two were used. I have no idea if it was an OE unit or not. My guess is that the other two terminals are for killing another circuit on some models.

The neighbor cooked the starter solenoid trying to start it (repeatedly). When I replaced that with an OE unit I noticed that the wire terminal going to the MPEM was very nice and shiney. New looking. Also, that same ring terminal did not look as beefy as it should....Right away I wondering if I was seeing China.....

I wonder what a new OE MPEM costs, or even if they are still available....I think your discernment is correct....China!

 

[burtshaver2021]

is there any chance it’s just the lanyard switch that’s bad? I don’t have a good understanding of them at all but is the original switch open, and the lanyard holds it closed to run? I thought maybe the new aftermarket switches were opposite, closed and the lanyard holds them open? . I know I read something about that. Not really sure. If your looking for good used parts people seem to have good experiences with Westside power sports @Minnetonka4me

 

[burtshaver2021]

Oh, I see what your saying. It may be an aftermarket MPEM

 

[burtshaver2021]

Updated PWC used parts & Salvage Yards
I would definitely give Nick a call at Westside Power sports. He will only send you tested quality used parts and if you talk to him, he may have some ideas as to to Your problem and will only sell you what you need.

 

[Ernest Jones]

Yeah, I'm quite certain we'll find it's not an OE MPEM. Previous owner probably threw out a perfectly good OE unit trying to troubleshoot something

is the original switch open, and the lanyard holds it closed to run?

Yes, having the lanyard in closes the circuit allowing the unit to run/crank etc. When you remove the lanyard it breaks the circuit preventing cranking/running.

The only way the switches could do this would be if a highly improbable situation occurred. Both switches went to ground on their own. Given it's very hot out, no rain etc, it has to be something in the MPEM. It's somehow grounding those two lines on it's own and then sending out the signal to close the start solenoid causing the cranking.

 

[burtshaver2021]

Yes, your right. hopefully a good used MPEM does the trick