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I have a 2009 Rzr 800 efi and have developed an intermittent problem. Took the machine on a 50 mile round trip and it ran great up tyo about the last 6 or 7 miles. It developed a small misfire and loose of power. never did shut down and got it back onto the trailer ok. Got it home and ran it around the block a couple of times and everything appeared to be ok. Ran smooth and plenty of power and acceleration. But decided to tear the fiberglass off from around the engine to be able to inspect and see if I could find an "ah ha" problem, which I didn't. Changed spark plugs and did a full service on the machine. Ran it around town for about 50 or 60 miles over the course of a week or so and no problems. Decided to take it on another short trail ride, about 20 miles round trip. Trail was extremely rocky but the machine performed flawlessly for the day. Yesterday decided to take a trip up one of the local canyons and again the machine ran fine thru town and part way up canyon. Pulled over for just a few minutes and when I tried to get rolling again the misfire and loss of power problem was back. Never shut machine off Could barely get it over 20 mph. Ran the machine this morning around town and it appears to be running ok again.

Yesterday while my brother in law was following, his wife mentioned she thought she smelled gas when my machine started acting up. I also smelled gas shortly after we started the ride before the problem surfaced, but I had just fueled up so I dismissed it. This morning I was paying particular attention to any smells and although it was running good there was a small hint of gas smell. I also noticed that even though the ride yesterday was about 10 miles that I had used a significant amount of fuel. Way more than what has been the norm in the past.

Anybody have similar problems and what was the verdict? I am thinking it is fuel delivery problems because of the usage and the slight smell. Are the fuel injectors a possible? I am an automotive/heavy truck mechanic but not much experience on these smaller engines. Machine was bought from a family and was never used in hard core or extreme conditions and has about 3,000 miles on it
 

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I have a 2009 Rzr 800 efi and have developed an intermittent problem. Took the machine on a 50 mile round trip and it ran great up tyo about the last 6 or 7 miles. It developed a small misfire and loose of power. never did shut down and got it back onto the trailer ok. Got it home and ran it around the block a couple of times and everything appeared to be ok. Ran smooth and plenty of power and acceleration. But decided to tear the fiberglass off from around the engine to be able to inspect and see if I could find an "ah ha" problem, which I didn't. Changed spark plugs and did a full service on the machine. Ran it around town for about 50 or 60 miles over the course of a week or so and no problems. Decided to take it on another short trail ride, about 20 miles round trip. Trail was extremely rocky but the machine performed flawlessly for the day. Yesterday decided to take a trip up one of the local canyons and again the machine ran fine thru town and part way up canyon. Pulled over for just a few minutes and when I tried to get rolling again the misfire and loss of power problem was back. Never shut machine off Could barely get it over 20 mph. Ran the machine this morning around town and it appears to be running ok again.

Yesterday while my brother in law was following, his wife mentioned she thought she smelled gas when my machine started acting up. I also smelled gas shortly after we started the ride before the problem surfaced, but I had just fueled up so I dismissed it. This morning I was paying particular attention to any smells and although it was running good there was a small hint of gas smell. I also noticed that even though the ride yesterday was about 10 miles that I had used a significant amount of fuel. Way more than what has been the norm in the past.

Anybody have similar problems and what was the verdict? I am thinking it is fuel delivery problems because of the usage and the slight smell. Are the fuel injectors a possible? I am an automotive/heavy truck mechanic but not much experience on these smaller engines. Machine was bought from a family and was never used in hard core or extreme conditions and has about 3,000 miles on it
Since you are a mechanic you can check the fuel pressure pretty easy. I'll guess the pump is dying.

I'm a retired auto tech and I don't recall but maybe 1 or 2 failed injectors on gas engines over my 30 plus years of my career. I'm thinking these are the same, very unlikely it's a bad injector.

As you know intermittent things are the hardest to diagnose. I've seen quite a few posts about dying fuel pumps so I don't think I would chance breaking down in the middle of nowhere over the pump. I would replace it just because. Remember it not just 3k miles, it's ten years old now too.

Maybe someone can recommend a good place to get them, I think Polaris will bend you over big time and maybe even want to sell you an entire tank/pump assembly from what I've read on some Rzrs.

I remember talk of gas caps and tank vents getting plugged up too, causing vacuum in the tank. I've never really looked close at mine but maybe you can clean and test it.
 

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Discussion Starter #3
I did run a fuel pressure test and after the tester was purged of air I had 39 lbs both with just ignition on and at idle. But as I has stated in my first post machine seems to be running ok. Guess I'll drive it around with the pressure gauge still on and see if I can get the problem to surface again.
 

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I got the problem to resurface where I could run some diagnostics on it. I believe I have a lifter starting to fail. Had a ticking noise that I was able to pin point to the area of the engine where the lifters are and alone with loss of power and rough running I was starting to get back fire. Guess Ill find out when I tear down the top end.
 

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I got the problem to resurface where I could run some diagnostics on it. I believe I have a lifter starting to fail. Had a ticking noise that I was able to pin point to the area of the engine where the lifters are and alone with loss of power and rough running I was starting to get back fire. Guess Ill find out when I tear down the top end.
Backfire too? Oh no. Good luck hope it's not to deep. Sounds like it could be a valve though. Bummer.
 

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Discussion Starter #6
Getting to the lifters wasn't very hard at all. To get the head and cylinder off didn't have to pull the engine. Still haven't found an "ah ha, that's the problem" thing, but then the problem has always been intermittent. The valves, valve seats, rocker arms, push rods and combustion chamber all look good. Not much carbon build up and the valve seats do appear to hold a seal. Still thinking a lifter going bad because of it being intermittent rather than something worn or broken. Problem only surfaces after the machine has been ridden for awhile. Last time it happened and when I got it home I didn't shut the engine down and grabbed my stethoscope and definitely was able to locate the ticking noise as being right there at the lifter area of the engine case and it was definitely towards the #3 or #4 lifter.
 

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A little hard to do now, but I would check oil pressure while driving. See if intermittent problem is related to oil pressure.
 

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Discussion Starter #8
A little hard to do now, but I would check oil pressure while driving. See if intermittent problem is related to oil pressure.
That is one thing I didn't really think of before hand. But with my experience with automotive engines when you loose oil pressure you have more than just one lifter making noise. Pretty sure I could detect only one lifter making noise. I'm pretty old school and I really do prefer gauges and was thinking on adding a pressure gauge anyway.

Just a dumb question, but the factory service manual refers to a blind plug/sender on the "left" side of the crankcase. A quick look around I couldn't see what it refers to. As far as left side, where are we standing. The front, rear, driver or passenger side.
 

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There is a 1/4"-18 pipe plug in the oil galley, that can be used for a gauge or sender.
Number 11 in drawing.

2019-09-07_111722.jpg
 

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Discussion Starter #11
A little hard to do now, but I would check oil pressure while driving. See if intermittent problem is related to oil pressure.
Another quick question about the oil pressure possibility. Is this a problem with this model machine as far as history goes? Haven't done an extensive search, but have yet to really find anything as far as a weak point in this model of engine.
 

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The pressure relief valve (PRV) is problematic. I think they should be dissassembled and cleaned every several oil changes.

Search the Forums for PRV.

2019-09-12_091249.jpg
 

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Discussion Starter #14
The pressure relief valve (PRV) is problematic. I think they should be dissassembled and cleaned every several oil changes.

Search the Forums for PRV.

View attachment 584030
WOW, there is alot of discussion about the PRV's. Like previously stated I'm an automotive/heavy truck mechanic so these little engines are a new learning experience. Lots of discussions and ideas about the PRV and adjustable PRV's. A Particularly long one by "allcool" I pretty much follow the logic behind everybody's thoughts, but they some of it is really confusing. As much as I want to pull my PRV out and inspect/clean it while I have the engine down, I think I am going to leave it in until it is running again so I can see where my pressures are at currently. Have installed an oil pressure gauge and I'm running the polaris 5w - 50 oil.

I noticed your posts about your home made PRV and did see your posted data. But whereas that thread is several years old, what are your thoughts about your home made PRV and are you still running it. I do have a small lathe and machine shop at my place so making one for me would be a no brainer.
 

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Rob,
I like your plan. I would leave PRV as is untill engine is running, and see what the pressure is at start up, and when running at temp.
I did not like how low my RZRs pressure was at idle, when at operation temps.
I am still running adjustable PRV, and liked the fact that I can dial in pressure for oil type & weight, filter brand, and operating temperature.
Once I got pressure set, I have not had to re-adjust.


NOTE TO OTHERS, Follow this link for more info on adjustable PRV build: https://www.rzrforums.net/rzr-800-specific-discussion/331473-looking-adjustable-oil-pressure-relief-valve-prv-post4042881.html#post4042881
 

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Discussion Starter #16 (Edited)
Got the engine back together. Haven't had a chance to drive it around yet to see if the problem resurfaces being it was a problem that only occured after then machine had been driven for awhile. I had approx 40 lbs oil pressure on initial cold startup. After I believe that the oil was at or close to operating temp (207 degrees taken on the oil filter), my idle pressure was 15 lbs and at 5500 rpm's I was just under 40lbs. With this work on the engine, and being more old school, I added oil pressure and temp gauges so I could monitor while driving. I will post again after I have driven it a bit to see if the problem re occurs.
 

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