Polaris RZR 900 Running on One Cylinder
Our 2015 Polaris RZR 900S had been sitting in storage for a while, and when we brought it out, it seemed to run fine at first. After a while, however, it started intermittently losing one of its cylinders.
Is it a fouled out spark plug? Maybe one of the coils has gone bad or the fuel injector for that particular cylinder is clogged up. Watch the video above or read on below to learn how to troubleshoot a dead cylinder on a Polaris RZR 900S.
See the parts diagrams: Polaris RZR 900 parts
Tools and Parts - Polaris RZR 900 Troubleshooting Dead Cylinder
- Ratchet and extensions
- Spark plug sockets
- Spark plugs
- Polaris air filter
The spark plugs in our Polaris RZR 900 weren’t completely fouled out. And while they still could be the problem, it was beginning to look more like the fuel injector for the faulty cylinder was to blame.
Check the Air Filter
Before checking on the fuel injectors and replacing the spark plugs, we opened up the air box to check on the condition of the air filter, since it had been sitting for so long. We covered up the spark plug holes before opening up the airbox so no dirt or debris falls in there. The air filter was filthy, so it was time to go ahead and replace it.
We cleaned out all of the dirt and debris inside the airbox and installed a new air filter, which needs to be pushed all the way in on the back section until it grabs in place.
Replace the Spark Plugs
Even though the spark plugs appeared to be in decent shape, spark plugs are cheap and should be replaced anyway. Whether the new spark plugs need anti-seize lubricant on them or not before installing them is debatable, but we went ahead and added some before installing them and torqueing them to 7 foot-pounds.
After installing new spark plugs, we fired up the Polaris to see if new plugs and an air filter made a difference. While the UTV sounded better, it didn’t solve the problem, so it was onto the fuel injectors.
Check the Fuel Injectors
To access the fuel injectors, we first needed to get the fuel rail out of the way.
We removed the T20 and T30 Torx bolts that hold in the fuel rail, disconnected the fuel line, removed the fuel rail and took out the fuel injectors for each valve.
NOTE: Have a rag ready while disconnecting the fuel line from the fuel rail, because the fuel line probably still has pressure in it.
Once we pulled out the fuel injectors, we used a cotton swab to carefully clean around them so as to not push any dirt or grime down into the intake.
NOTE: Be extra careful not to drop a cotton swab down in there, because it could fall straight into the engine and do some damage.
Clean the Fuel Injectors
When it came time to clean out the fuel injectors, we went with a fuel injector cleaner kit from Motion Pro, a tool that comes with several pigtails to accommodate several types of fuel injectors.
We used the fuel injector cleaner kit and some Honda carb cleaner spray to clean out both fuel injectors. However, the fuel injector cleaner kit wouldn’t activate for one of the two injectors, which meant that it needed to be replaced.
NOTE: We used Honda carburetor cleaner here, but Motion Pro also makes a fuel injector cleaner spray you can use.
We found during the fuel injector cleaning process that one of the two fuel injectors was faulty, so we decided to just go ahead and replace them both. Before installing the new fuel injectors, we sprayed a little bit of fuel injector cleaner on their O-rings just to make them easier to slide in.
Watch the video below to learn how to clean fuel injectors with the Motion Pro fuel injector cleaning kit.
Reinstall the Fuel Rail
We reinstalled the fuel rail, then reconnected the fuel injectors and the fuel line.
Once everything was back in place, we primed up the fuel system a couple of times to hear what the machine sounds like, and replacing the fuel injectors solved the problem of why our Polaris RZR 900 was only running on one cylinder.
