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2007 M8 dies, won't restart

kbroderick

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So i've been trying to troubleshoot a pesky 2007 M8 since Saturday afternoon. short version of symptoms: it will stall out and refuse to restart. Troubleshooting on Saturday confirmed that it has at least some spark, fuel at the rail is under pressure, and it definitely has compression. Since then, it's generally been happy to start in my garage but not in the field, and when it does die in the garage, it will idle up to about 3300k, stay there briefly, and then drop steadily to about 1200 when it dies. Unplugging the handlebar or hood harnesses don't seem to affect much. Unplugging the temp sensor let it start up when it wasn't wanting to but then resulted in a highly variable idle and the sled dieing.

Long version below:

I bought this and an 08 M8 on friday, rode from the Pilot lot into Cooke City Friday night, and used them for sled skiing Saturday morning. Around 12:30 - 1:00, snow was starting to get a bit sketchy on anything steep enough to ski, so we decided to ride around and explore a little; I got a little over-excited, hit a tree with the '08, toasted the left-side a-arms, and buried it pretty well by the time we got it disentangled from the tree. By the time we had it dug out, the '07 (which until this point had been happy) had probably been sitting about 45 minutes to an hour. My friend went to pull the '07 around with the idea of helping pull the '08 out of its hole, and it stalled out and died.

At that point, I pulled two of the more-accessible plugs, which were wet but otherwise looked good. In case of any sort of flooding or vapor lock, we pulled it over with the plugs out, confirmed it had spark, and put them back in..at which point the next pull fired it up. A couple other guys stopped by and helped pull the '08 out by hand.

My friend rode the '07 back to town, while I skied back, meeting her when things got flat and getting towed back in. It ran fine until I hopped on it at the paved end of Main st., at which point it stalled outside of Bearclaw Bob's. Got it going again a little later, made it almost to the Exxon; and then the last time was about ten feet or so. We let it sit overnight, no joy in the morning; it seemed to have at least weak spark, definitely had fuel pressure at the rail, and had compression. I pulled the belt and we towed it back to Pilot.

Sunday night in my garage, my roommate noticed the ignition trim ring was loose; we thought perhaps the key hadn't been clicking all the way to on, as the sled ran fine in the garage after tightening that. Monday night, I tried to take it out locally, and it ran on the trailer almost long enough for me to get my helmet, goggles, glove and pack on (probably 2-3 minutes) before stalling out and dieing.

With no changes since then (it had been sitting, covered, on my trailer), it didn't want to start. I unplugged the (unused) accessory wire sensor near the ignition, it started, revved high (around 2500 RPM), drops below 1800 and dies after about 45-60 seconds.

Plugged the plug on the accessory wire back in, fired it up, let it idle for two minutes during which it stayed at 1700-1800 for 2+ minutes.

Tried wiggling handlebar, no effect.

Tried hitting warmer controls, revved up near 3300, dropped low (1200ish) and died.

Pulled it over, it fired up, revved up near 3300, dropped low, and died.

Thinking something on the bars was responsible, I unplugged the handlebar harness, restarted, and let it idle for about three minutes (around 1700-1800 RPM the whole time).

I reinstalled the bar plug, pulled it over, and it idled fine for over a minute and a half.

I tried changing the heater switches, first one than the other, with no changes.

I tried turning the bars to the left and it repeated the high-idle, drop low, die routine.

I turned off the heaters again, revved high and died.

Then I unplugged the handlebar harness...and again, it started up, revved to around 3k, dropped below idle and died.

Any thoughts? I'm planning to start checking resistance on coils and the like, but this seems a lot more wonky and intermittent than a simple ignition fault.
 
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kbroderick

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Following up on my own post, I just checked resistance on the stator from the connectors on the right side of the engine bay:
L1: 7.5 ohm (spec 7.2 - 10.8)
L2: 7.5 ohm (spec 7.2 - 10.8)
L3: 15.4-15.5 ohm (spec 15.2 - 22.8)
L4: 1.1-1.3 ohm (spec 1.52 - 2.28)
L5: read 0.0 - 0.2 ohm (spec 0.078 - 0.132), but I think that's a limitation in my multimeter
L6: 186 ohm (spec 185 +/- 20%)
L7: 185.9 ohm (spec 185 +/- 20%)

L4, the fuel injection coil seems to be out of spec, and L1, L2, L3 are barely within spec. Based on that, I'm thinking I should replace the stator; any other thoughts?
 

kbroderick

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Replaced the stator with one from RMStator last week, sled idled in my garage fine for 5-15 minutes before I put it back on the trailer, got back out to Cooke today. Sled ran fine for my roommate about three hours (riding in from Pilot to Lulu, playing a bit a little ways up Lulu trying to learn how to get the sled to actually bank and turn, and then playing a little more while I was hiking and skiing one of the Rasta chutes), then died again.

It seems to have good spark; neither unplugging the intake air temperature sensor nor installing new plugs solved the problem, although both allowed it to run briefly.

For electrical troubleshooting, the service manual says:
2. Disconnect the main wiring harness connector coming from the engine stator assembly. Disconnecting this connector will bypass the main wiring harness and all switches which will not allow the engine to be shut off without first installing an additional auxiliary ground wire.

3. Insert an auxiliary ground wire into the black wire of the four-wire main harness connector on the engine side. To stop the engine once it has been started, touch the auxiliary ground wire to the engine.

Which one is this? Looking at the wiring diagram, I can't tell which connection from the stator I could pull without affecting something (e.g. fuel pump or ignition) that would keep the sled from running, and I don't see any four-wire connectors with a black wire, either in the wiring diagram from Mowparts.com or on the sled itself.

Two more data points, which may or may not be relevent:

1. my roommate thought the sled seemed like it was running lean, and it does have an aftermarket intake (not sure of the brand), y-pipe (Speedworx) and exhaust on it.
2. Riding from Pilot into Cooke on the unplowed (but packed) roadway, the sled did show a temperature warning light, at which point my roommate stopped and deployed the scratcher. My '08 didn't show any warning lights at the same point, having ridden the same distance on the same snow at about the same speed, but I did deploy my scratchers as well just to be safe. On the way back out, towing the '07 with the '08, I didn't deploy scratchers but also didn't get any warning lights (granted, the snow had softened and may have been more effective for cooling).

Any thoughts or suggestions appreciated; I'm having a bitch of a time troubleshooting this given that it seems to only fail reliably after several hours of riding time.
 

kbroderick

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I haven't had time to wrench on it any further since trying to get it running again during Saturday's outing, but even after sitting on the trailer for three days, it still wouldn't fire when I pulled it over today. I think that should rule out heat-related issues, but I'm not sure.

Further investigation does indicate that the secondary coils are loose on their mounting points; the inserts from the bottom of the tunnel are loose, and they can rattle around. This seems potentially problematic to me, but it seems peculiar that it would create an issue only after a couple of hours of riding if it were the issue.
 

kidwoo

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I'm going to bug you over here because it might be more productive. Skiers don't know **** about sleds. :face-icon-small-ton

Find that fuel controller. If you don't have one that's a problem with that pipe, unless there's something unusual about the 07s. If the guy you bought it from ran it without a controller, it's probably been running lean. If/when you do find it, follow the wires and look for a ground. Make sure it's good. Make sure the connections where it intersects the main harness are good.

If you're still getting spark on the plugs coming from the coils that rattled loose on the mounts I wouldn't sweat it. Just get them back solid on the front of the chassis.
 
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kbroderick

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I'm going to bug you over here because it might be more productive. Skiers don't know **** about sleds. :face-icon-small-ton

That's clearly true in this case, but I'm learning fast. :noidea:

Find that fuel controller. If you don't have one that's a problem with that pipe, unless there's something unusual about the 07s. If the guy you bought it from ran it without a controller, it's probably been running lean. If/when you do find it, follow the wires and look for a ground. Make sure it's good. Make sure the connections where it intersects the main harness are good.

If you're still getting spark on the plugs coming from the coils that rattled loose on the mounts I wouldn't sweat it. Just get them back solid on the front of the chassis.

Copy that. I've got a stock intake on order, which will be going on when I get back from a ski trip next week. The coil mounts look to be a PITA to get at, as the inserts from the bottom seem to be loose and I couldn't reach them from below when I last tried due to the track.
 

kbroderick

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Just to follow up:

a) no fuel controller is present. The sled probably is running lean, and it definitely runs a little hotter than my '08 M8 (in scratcher-use-needed conditions, the 07 will start flashing the warning light before the '08 if both are run without scratchers up the refrozen trail at the same speed)

b) I did reattach all the coils to the tunnel (using fender washers to sandwich the tunnel and through-bolting them)

I didn't get out as much as I was hoping this year, but never ran into the same issue again, so I'm thinking that somehow the loose coils were creating some sort of electrical (grounding?) issue. I did not end up installing the stock airbox, after realizing exactly how much space that would take up under the hood and how much of a PITA it was going to be to get everything back together afterwards.
 

nelsonhouse

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Fuel injector

I had a similar problem. I stopped to cool off my m8 and it did not want to start up after cool down. I had the sled towed home by some good friends. I pulled the plugs and they where a bit wet. Flooded was my guess. Pulled it over a couple times with the plugs out. Put the plugs back on and it fired up. Took it for a short ride and turned it off. When I went to start the sled about ten minutes later. It would not start. I pulled the plugs and they were wet again. It was flooded again. I tipped the sled over on it’s side and pulled it over a couple times and more fuel came out. It was flooded for sure. Tipping the sled over and pulling it over clears out the flooded engine a little quicker btw. I remembered my brothers zr900 had the same problems with flooding last year. I took the my m8 into my shop. I Removed the fuel injectors and cleaned them out. And the sled ran perfect after cleaning injectors. It ran even better than before. The four screws you need to remove strip easy. Be careful with them.
 
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