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Help Intermittant problem

rcr1978

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Dec 24, 2007
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Spring Creek NV
My sleds a 07 M8, please ignore the mods in my sig cause I had the same problem before I put them on. My sled will start an run fine and run perfect for about an hour then sometimes it will get a off idle bog bad enough to stall. The other problem is sled wont start after I shut it off until it cools down about a 1/2hr, or it will start but barely run around 12-1600 rpm as soon as the throttle is opened it immediatly dies. If I unplug the coolant temp sensor all problems are gone the sled will start and run fine. I got a coolant temp on order just want to get some other ideas, already replaced TPS, checked all wiring everywhere at least 4 times tore the whole sled apart checking wiring, unhooked throttle safety switch, injectors check good, all stator coils check good, fuel pressure holds at 46psi gauge is in site at all times. My AFR gauge goes way lean when this problem happens, still have spark.

Anybody got any suggestions it sucks throwing parts at a sled gets expensive in a hurry.
Thanks
Robert
 

rcr1978

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Dec 24, 2007
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Spring Creek NV
I think the turbo guys have the exact same problem with the coolant temp sensor, no start then unplug start and plug in again and all good again? I don't understand :face-icon-small-con
 
D

diggerdown

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Apr 25, 2004
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Deer Park Wi.
I think you got it covered with the coolant temp sensor. If that does not work, check the air temp sensor and the external spark plug coil. A common thing with coils is to work for a while when cold and reduce voltage or stop working when they heat up.
 
J

JHG

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Jan 29, 2008
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Elizabeth, CO/Bozeman, MT
It's probably just a failing temp sensor.

What happens is, when you shut your motor down after a hard pull or riding, the water pump quits moving water through the motor. The motor sits and transfers all of it's built up heat to the stagnant coolant that's in the motor. When the coolant gets to hot, it trips the temp sensor. With the bypass switch you interrupt the temp sensors signal to the ECU, making the ECU think everything is good. The sled starts, and the water pump starts, moving the hot coolant in to the heat exchangers and cool water back into the motor. The temp sensor resets with the cool water, you reconnect the sensor to the ECU and you're good to go. In the turbo world, we run the motor harder and hotter and in many cases the coolant passes though the turbo, picking up lots of heat. If you don't let the sled cool down at idle after a hard pull, the motor will heat soak. There's a little more to it than above but that's the cliff notes version.
 

rcr1978

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Spring Creek NV
Thanks for the replies guys, my temp sensor showed up and I'm putting in tomorrow not enough snow to test it hard though since it warmed up this week. Do the turbo guys have the temp light come on when they have the problem?
 
D

diggerdown

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Apr 25, 2004
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Deer Park Wi.
The temp light only comes on when it thinks the temp is too high. What is happening is the temp sensor is just reading a temp higher than what is actually there, and adjust the fuel delivery in error.
 

rcr1978

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Spring Creek NV
Just reporting back the coolant temp sensor did not fix my problem, but if I unplugg it still it will start and if I plug it back after a few minuets of riding the problems gone for another hour or so. It is worse in deep powder, I guess I'm gonna put a switch inline with the coolant temp sensor for now untill I can find the actual problem, guess intake air temp sensor is next on the list this sucks changing parts :mad:.
 

rcr1978

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Spring Creek NV
I've had it apart at least 3 times looking for chaffed or shorted wires, they all look good and I fixed all possible future problem areas that looked like they could cause problems. :confused:
 

mmsports

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Get a fuel presure

Couple of things. Put fuel pressure gauge to see if you are loosing pressure. second get a 9V batteries so as you can hook voltage up to pump. This is my thoughts is that the part of stater the runs your fuel pump is going bad.
 

rcr1978

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Spring Creek NV
My fuel pressure gauge is in constant view I mounted it on the cowling by the pull rope, no fluctuation. Thanks though any more ideas?:
 

rcr1978

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Dec 24, 2007
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Spring Creek NV
Here is another weird thing, when its acting up the little throttle percentage display on my power commander is showing about 30% at idle. Now before everyone thinks after market problems this problem started before all the aftermarket parts. TPS is brand new and adjusted correctly. When no problems the little display reads normal. I'm thinking its a CCU problem power related to the ECU but I'm really reaching now to figure it out.
 

rcr1978

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Spring Creek NV
I checked the resistances of all stator coils already and they checked good. I even took it a step further and megged them and still good. I'm at a loss?
 

rcr1978

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Well thanks everyone for all your sugestions, Im getting my ECU reflashed again tomorrow to rule a bad reflash If I remember correctly the problems started after my 08 reflash. If it still is not working I have a couple friends with M8's and a M10 to swap parts with ECU, CCU, and the rest of the sensors that are easy to get at if that don't get it then I'll try a harness. Still putting a switch on the coolant temp sensor so I dont have to wait for my sled to stop its period and decide to run. I will report back when its fixxed I think there is a few others around with the same symptoms I read about.
 

rcr1978

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Dec 24, 2007
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Spring Creek NV
mmsports, thanks for all your suggestions. I agree with you on the stator, I checked it cold and unit runs great until good and hot so I'm not ruling it out just want to exhaust all other options without spending $$$$ freakin parts are expensive and I just want it to show its self without throwin parts at it. I hate being a parts changer it adds up fast, could buy a new sled or turbo or something instead. :face-icon-small-coo
 
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