2011 RZR Runs on one Cylinder

Jorg Jorgenson

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Hey guys, so at the beginning of this summer some of you may remember my first post as I had just purchased a 2011 RZR 800s. Had a flawless summer except for the over the September long weekend when my brother was out riding and said it started to occasionally drop out on one cylinder. They would turn the machine off to let it cool down, turn it back on and get a few more km's down the trail before it would start happening again. Sometimes wiggling the plug cap/wires would help (so they say, as I was not there). Had to limp it back for a good hour to the cabin like this. I have since taken the machine apart and have done the following tests w/ results below:

The MAG (more towards the back of the machine) side plug was soaked and black (it had been sitting and not running for a few weeks). The PTO side (more towards the front of the machine) was dry and white. So already both not ideal cases. bought new NGK plugs right away and started it to get the machine up to temp before driving. After a few minutes of driving, it would gradually lose one cylinder firing. I left it idle and pulled the spark plug caps off to discover that it was the MAG side that would drop out (which matches up with the soaked plug). I switched the spark plug wires that go from the coil to the plugs around to see if the issue followed the wires or the cylinder & performed the same test. It remained the MAG side that would not fire after getting up to operating temp. I then tried switching around the plug caps only, leaving them connected to the coil as they were originally, just to see if if the problem would remain on the MAG side or switch to the PTO side assuming I have an issue with the coil. The machine wouldn't fire in this condition due to the timing now being off as they are set up from factory to not be switched around. Was worth a try I thought.

I then did a compression test to see if there was something fundamentally wrong with one of the cylinders. Surprisingly, the MAG side checked out as about 172psi and the PTO side was 150psi. So I now feel like I have another issue to deal with once I get the MAG side firing again!

Has anyone else had a similar condition happen? I've done some research and it sounds like an almost exact situation where it turned out to be a bad coil. I currently have new spark plug wires/caps on order and a new coil to try sometime next week. Any advice/suggestions are welcome! Trying to get this fixed to I can park it and focus on getting the sled back together lol.

Cheers,
Jorg
 

the_real_wild1

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Sounds like you are on the right track. If one of those three don't fix it then I check on the rzr forum.
 

tex78

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Coil gets hot and quits on the one cylinder it sounds like to me
 

Jorg Jorgenson

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That was my theory too Tex hence why I have a coil on order now to try. Any comments on the varying compression values though? The 172 does not alarm me but the 150 does.. coukd an injector be stuck closed making it run lean and burning white hot? Has Anyone else experienced values like this? My suggest fear is that I have an engine on its way out the door
 

Summitric

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was the compression test done with the throttle wide open? did you do a wet and dry compression? cylinder could be washed down from fuel , because its not firing and as a result, will have a lower compression.
 

Jorg Jorgenson

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was the compression test done with the throttle wide open? did you do a wet and dry compression? cylinder could be washed down from fuel , because its not firing and as a result, will have a lower compression.

Yes I stepped on both the gas and brake pedal so the engine would spin. Took the cap off the one plug and then threaded in the tester into the other side. Turned the key for 5 second Count. I'm not sure what the difference is between a dry and wet compression test though??

Oddly enough It was the cylinder that has always been firing which has the lower compression, the one where I pulled the soaked plug from has the higher compression.
 

CatMan16

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You should have both plugs out when testing the compression.
 

Jorg Jorgenson

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Ok so finally got around to putting on the new plug wires and coil. No change in results, still the MAG side will drop out and it runs on only the PTO side cylinder. Now open for more suggestions!
 

Jorg Jorgenson

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And for what it's worth, I will on my next attempt (prob later tonight) i unplugged the cable running to the battery that powers up the speakers, interior lighting & light bar (all done by previous owner) in case there is an electrical issue that is being passed down from any of these. He did a nice job with installing a fuse panel w/ independent fuses for everything in the hood compartment so I doubt this is causing any issues but just to be on the safe side maybe worth disconnecting...:confused: I'm really as a loss on this one though guys. I'll also re-try the compression test as you suggested CatMan
 

Jorg Jorgenson

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I wanted to give let everyone know that the SXS has been fixed and all is running as it did earlier in the year. Thought I would share my experience since the 'culprit' is actually quite embarrassing for me to admit but hoping this helps others with a VERY SIMPLE fix to my issue.

I ended up taking the RZR in to Cycleworks 75th street in Edmonton, worked with the guys in the back on a Saturday ran through an engine diagnostics test compression leak-down test hooked up a timing light to injectors & checked fuel pressure all well within spec.They decided to keep it & look at it again on Tuesday after the weekend. Ruled out the possibility of a mechanical issue since it only dropped out on one cylinder after getting up to/close to operating temperature.They were all stumped and could not figure it out.

Some background info... while I was trouble-shooting in my garage, I went ahead and did a full fluid change. Decided not to change the oil until I had my issues figured out, I did notice that it was low but since I was not driving it I was not concerned and was going to drain it all out and replace anyways.

Back to the story... so the guys at the shop pulled the dipstick and saw the I was low on oil. They added some in, fired it back up and could not get the problem to re-occur. My fix... adding more oil. Reason being, since the engine is designed with hydraulic lifters it relies on the oil pressure to operate the lifters and provide a proper air/fuel ratio for combustion in the cylinder (so I was told). I'm sure the mechanic's on this site will better understand this principle than myself so I won't try to make me sound like an expert, but it was a very simple fix. I hope that this can help others save time & money if they are experiencing a similar issue with their RZR. Spent $650 in the process with electrical upgrades but at least now I for sure know what I have for next year!!:beer:

Cheers
 
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