I've been chasing ghosts on my 05 Sportsman 800 EFI for some time now. The machine is mostly used around my 5 acre property and is frequently stopped and started on short trips less than 5 or 10 minutes long. My primary issue is that I'm definitely getting fuel into the crankcase, causing the level to slowly rise until it becomes necessary to change the oil because of the high level and concerns of the oil losing lubricity thru dilution. So here is a little background:

• TBAP harness has been upgraded and fuel pump/regulator has been replaced.
• The quad runs great with no smoking and as much power as it had when I bought it new. It does foul one plug pretty often.
• My thinking is, if fuel is getting to the crankcase, it's getting past the rings. So, after checking compression on both cylinders, one cylinder was reading lower than the other. 145# vs 160#. It was suggested I may have a stuck ring on the offending piston and that letting them sit overnight with a couple of ounces of Marvel Mystery Oil on top of them might free the ring. I did this three times, letting the MMO sit on the pistons for 24 hrs and saw significant improvement afterwards. Compression on each cylinder improved to 170ish on each cylinder! Mission acomplished right? Wrong. Oil level still climbing at the same rate as before.
• OPT suggested I take it to the dealer so I did. The dealer checked it with the electric wrench which did not identify any problems. They also re-flashed the computer with latest flash and performed a leak down test. They basically said the leak down test was borderline and that it needed a new cylinder and pistons which they would be happy to install for a couple grand, or even better, they would sell me a brand new machine
• Well, that prompted me to do some research and order a new cylinder and pistons which I installed a few weeks ago. Yee ha. Thanks to some excellent YouTube videos, that entire process went well. Compression now at 192# on each cylinder. Mission accomplished, right? Wrong. No change on the oil issue. I cleaned up the valves and seats with Scotch Brite during this job and they looked good to my untrained eye. I wish now I had replaced the valves and lapped the seats. Rods, lifters and rockers were all returned to their pre-job locations as they all looked like new with virtually no wear.
• It was suggested that I likely had an injector leaking by allowing unburned gas to depressure into the cylinder every time the machine was shut off. I tested the fuel pressure. When I turn the key on the pressure jumps up to about 37# the bleeds down to zero. When the engine is running, it maintains 37# regardless of RMP. As soon as I shut it down, the pressure falls to zero. So, I'm thinking I have a leaking injector. I replaced both injectors with brand-spanking-new ones which didn't change a damn thing.

This is where things stand now. At this point, I can't let this machine beat me. I'm gonna get to the bottom of it no matter what it costs. Believe me when I say, ANY help or suggestions will be very much appreciated.

 

You have a tough one it seems. As far as the fuel pressure dropping, I would guess the fuel pressure regulator. My reasoning is its not available through polaris new but can be bought online(so my guess is its an aftermarket regulator and not and OEM.) That fuel system consists of a tank, pump with screen, external filter, fuel rail, and injectors. The only item that is closely related to both fuel and motor, is the injectors, so it seems that would be the likely area for fuel leakage into the cylinder(but you stated you changed those) Question, were they OEM or aftermarket? Could make a difference if aftermarket. Not all parts that "FIT" what they say they will, are good quality(especially aftermarket) Some are good though to.

I would think you should possibly be able to see if the injectors are leaking by just removing them, leaving them hooked up to the fuel system, and cycle the key. WE have used that method on some John Deere gators in the past and found our issue.

It makes me wonder if the short trips have something to do with it like the motor not getting warm enough for the fuel to burn completely? Just a thought is all, cant say as I have ever seen it.

 

Thanks for the reply 94harley. You are correct in assuming that the fuel pump/regulator assembly are aftermarket. The pressure regulator could very well be the reason for the loss of pressure. But if so, that seems like it would be a good thing as far as my oil problem goes. I would much rather the fuel system depressure back to the tank as opposed to leaking thru the injectors into the cylinders. The injectors were aftermarket as well. They looked the same externally and were advertised as direct replacements for this engine and from a reputable parts dealer. The only thing holding the injectors in the fuel rail is the fuel rail mounting bolt. I wouldn't think they would stay in the rail to test for leak-by with the rail unbolted from the head and 37# on the upstream side. I'll try to figure out a way to test them before I go purchase new OEM injectors though.

I've used this machine for years without problem until this issue started. The short duration rides never caused this problem before. Something has changed and I obviously haven't been able to to put my finger on it. What's puzzling is that the quad runs like a new one with full power and doesn't smoke or backfire when cranked.

 

If the regulator was a good idea to allow fuel pressure to drop back to the tank, the car and atv manufacturers would all be doing it. I dont think its part of your issue however, we have seen machines that will drop pressure but seem to run fine without issues.

There are a lot of "Direct replacement" parts advertised out there these days. Question is, is the quality the same is all I'm saying. You can buy a 500 plus dollar carb from polaris, or a 45 dollar carb off ebay and they are NOT the same thing. I havent seen a lot, but its a "Chance" of getting an "exact good" part. It may fit, but something is different to get the cost down.

We have tested injectors that way and they have never flown out of the rail. I suppose its possible but havent had that happen to us.

Im not saying these are your issues, just throwing a few ideas to at minimum, entertain. I have ordered new parts before and installed and the problem was still there.
Mentally I assume the problem isn't in the part I replaced(since its now new) only to find out the "New Direct Replacement" part wasnt sufficient for use.

One other possibility is a worn throttle shaft. I used to see them wearing a little and causing the TPS to give false readings to the computer due to the vacuum pulling on the throttle plate(example- The computer thinks the throttle is at say 5 or 10 % open, when it is actually against the idle stop) A rich condition would occur in my opinion. When the throttle is opened, pull(vacuum) on the throttle plate decreases and possibly the TPS reading is close enough to run decent(or since when its opening the unit is accelerating and a minor difference in the TPS isnt noticable) I would have thought the digital wrench that was hooked up to it would have caught that scenario though. The other bad thing about this particular issue is there are very special tools to adjust the TPS, so most everybody wouldnt be able to even check it.

Try this if you like - Remove the air intake boot and start it and let it idle. Push on the throttle shaft(on the TPS side) with your finger, without opening the throttle plate, and see if the idle possibly changes. If so, throttle shaft is possibly worn a little.

Personally I dont think I've ever ran across what is happening to your machine, but since you are still having issues and have gone to the extent you have, I thought I might just share some stuff I've seen before. Hopefully a phrase, or word will lead someone in a direction to help you get it fixed.

 

I'm no mechanic and definitely not a Polaris expert, so forgive me if I think out loud or am off base. I'm not trying to refute your advice, just trying to get my head wrapped around it and hopefully learn something. I'll try your suggestion on the throttle shaft and see if there's any play there. I may even take it back to the dealer and have them verify the TPS calibration.
Point taken on the non-OEM replacement parts. If my fuel # regulator is the culprit for my loss of pressure as soon as the pump is off, it might make the injectors a little harder to diagnose. What voltages should I see at the injectors? I may test the original injectors first. A pair of OEM injectors at the dealer is north of 300 bucks. I checked the injectors I just installed and they are made by Bosch.
Thanks again for the advice.

 

I have to apologize if I sound bad. I'm a very to the point blunt person. Everything i posted had no anger, or argument involved. Wife tells me I need to lighten up too!! Sorry for that if it came out bad in any way at all.

If the voltage at the injectors was off, I think you see a misfire of some sort, not to mention a check engine light, rather than a oil level increase issue.

 

Been drinking a few beers and forgot to put this as a reply. The fact that Polaris wants retail of more 300 bucks makes Ebay and Amazon a lot more appealing(not that I know where you bought them though, just seems to be the go to place for a lot of things nowadays). That can be an issue though because even though Polaris doesnt manufacture their own efi parts( in my opinion) doesnt necessarily make the knock offs perfect replacements. Price is a big factor these days for all of us, but from my experience on ATV's, not always worth it. That being said, since you replaced the injectors and it didn't change, my guess is the old ones are ok too.

 

No apology necessary dude, straight shootin' is just the way I like it My wife says the same thing about me too!

 

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