Running on only one cylinder.

BenCrockett · Mar 25, 2011

Ok, I need some help!

A couple months ago, during a ride, my sled (2005 RMK 900) began intermittently running on one cylinder. It became increasingly worse throughout the ride. I shut it down and the next day it ran great for about 30 minutes, then did the same thing. It is always the mag side cylinder that quits running. There seems to be spark to the cylinder. Here's a list of what I've done to try to remedy this:

Cleaned and flow tested the injectors
Inspected the fuel system, pump for degradation
New fuel filter
Updated TPS harness
New water temp sensor
New detonation sensor
New mag side coil, lead, and cap
New plugs
New intake boots
Cleaned exhaust valves and replaced bellows
Inspected the stator for cut or abraded wires (none)

Every time I put it back together, it runs great in the garage. I'll bring it up to temp and still runs great. Once I get out on the snow, it punks out. This morning I got it all put back together, went out to the snopark, warmed it up, and rode about 100 yards before the mag cylinder quit again. I am about to kill myself, the sled, or innocent bystanders. Please help, we are getting great spring snow and it's driving me insane!

BenCrockett · Mar 25, 2011

Also, never get any codes flashing. And as a side note, reverse stopped working this morning as well.

Z-Man · Mar 25, 2011

When it quits running did you look at the plugs to see if both of them are wet (getting Fuel)?

BenCrockett · Mar 25, 2011

Yep. Both wet.

94fordguy · Mar 25, 2011

When it is cutting out, is your charge indicator still reading normal voltage?

Z-Man · Mar 25, 2011

Just looking over your list, Did you checked the wires to the injectors? I had my TFI fuel computer fall into my clutch last week and it did what you are describing. After I removed the TFI box and reconnected the injectors it still ran like it was only hitting on one cylinder for a few minutes.

Also is there any chance you could have some water in your fuel?

BenCrockett · Mar 25, 2011

To be honest, haven't drained the fuel tank. Hadn't occurred to me that there might me water in the fuel! The sled is always stored in my heated garage, so I didn't think it was the problem. I'll drain everything out of the tank tomorrow and see...

BenCrockett · Mar 25, 2011

I've had the injectors disconnected several times and all the wiring looks to be intact. I've heard that having the injector leads crossed will produce similar symptoms, so I've been sure to connect them properly.

BenCrockett · Mar 25, 2011

@94Ford
I wish I had the presence of mind to look at the voltage while it was happening. I need to ride with some smarter guys! I'm not sure if there is a drop while the mag cylinder quits. Another thing to check...

94fordguy · Mar 25, 2011

BenCrockett said:
@94Ford
I wish I had the presence of mind to look at the voltage while it was happening. I need to ride with some smarter guys! I'm not sure if there is a drop while the mag cylinder quits. Another thing to check...

Often times when the Stator gets weak, it will cause runnability issues as the sled heats up - especially when under load and more power is being demanded from it. If you are getting fuel to the cylinder and compression is good, then you may not be getting enough power to spark both cylinders under load. I cannot explain why it would only be happening on the mag cylinder though, that is a mystery.

I would be sure to have a glance at the charge indicator on the dash the next time it happens, if it is reading low or the battery light is flashing, you have something else you can check. Typically a bad stator will function properly after it has a chance to cool.

I believe a bad Capacitor can also cause issues in the same manner... if it is not holding enough charge it can cause all sorts of funny runnability issues (again, usually shows a low charge level on the display)

Z-Man · Mar 26, 2011

Maybe this is a dumb question, but How did you determine it was the mag side cylinder and that it is not missing on both cylinders intermittently once it is hot?

BenCrockett · Mar 26, 2011

Once it runs crappy, I pulled the plug lead off one cylinder at a time. With the mag side disconnected it will still run exactly as it had once the problem arose. With only the mag side connected, it will not run at all.

Also, I did neglect to look at the charge level, but I do know that it doesn't get low enough to flash the red warning light.

I'm going to order a capacitor first (cheaper) and if that doesn't work then the stator.

Keep the ideas coming, this is my first Polaris so I'm a bit mystified.

Z-Man · Mar 26, 2011

gotta be either a spark or fuel issue on the one side. Start her up and see what the volts are doing when it stops running right. I would think it would miss equally on both sides if it was volt related though.

There isn't any kind of a fuel injection control box on there like a boondockers or a TFI is there?

cranktwister · Mar 27, 2011

Had a very similar problem,ended up pulling the fuel tank and pump,found at the very far end of the fuel lines where the second pickup is the plastic connector that makes the fuel line do a 180 back up towards the pump came apart,Looks like it was glued from the factory,Also had zip ties holding the lines close together.I almost put it back together but realized that the two fittings fit into one another.My symtoms went away for 500 plus miles,until voltage regulator rubbed through the wires and wiped out the ignition side of the stator.Anybody else have this plastic connector on the end of their fuel pickup assy.I have seen another assy but it was a solid piece of tubing that made the 180 at the end.Just a thought

BenCrockett · Mar 27, 2011

No fuel control box. When the problem first started, my first thought was the fuel pickup/pump assembly so I pulled it out and inspected it and could not find any damage, loose connections, or other problems. I will check it again, though, as I going to pull the tank anyways to inspect again for worn wires coming from the stator.

900Spartan · Mar 27, 2011

Do not underestimate the issues with ethanol blended gas...if not electrical...fuel delivery issues as a result of phase separation and H2O precipitation can happen in a very short time with unused gas.

BenCrockett · Mar 27, 2011

@Cranktwister

I got to looking at the fitting at the bottom of the fuel pick-up and mine was held together only with a zip-tie. The actual fitting was loose and I could get it to come apart slightly even with the zip-tie in place. Is this supposed to be sealed? As it is now, it definitely is not sealed and fuel could easily leak from this fitting.

@94Ford

I ran the sled up to temp this morning in the garage and did get it to crap out on the mag cylinder. The voltage meter never dropped or moved at all as far as I can tell.

Z-Man · Mar 27, 2011

BenCrockett said:
@Cranktwister

I got to looking at the fitting at the bottom of the fuel pick-up and mine was held together only with a zip-tie. The actual fitting was loose and I could get it to come apart slightly even with the zip-tie in place. Is this supposed to be sealed? As it is now, it definitely is not sealed and fuel could easily leak from this fitting.

Fix this first, there are no fittings or connections that should be loose in the tank.

BenCrockett · Mar 27, 2011

Does this 180 fitting at the bottom end of the fuel pickup serve any purpose other reversing the tubing direction? I'm thinking about replacing it with a one piece "U" fitting to eliminate any chance of it leaking in the future. Thoughts on this very appreciated.

BenCrockett · Mar 30, 2011

So...

Replaced the fitting at the bottom end of the fuel pickup with a one piece fitting, drained the fuel tank, put fresh fuel in (ethanol-free premium, like always), and ran some moisture remover in the fuel. Still no better. So I think I can rule out water in the fuel and the loose fitting being the cause.

Any more ideas? Still waiting on the new capacitor from my dealer.

Running on only one cylinder.

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