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Discussion Starter #1
Here's the story: I bought a 2007 AC F6 SnoPro a few years back at the end of the season; it started fine, as the previous owner was using it semi-regularly. The sled only had like 1,300km or something.

I rode it for about 700km that weekend, then I stored it for the winter in my buddy's trailer. Come the fall, I take it out in hopes of giving it a once-over before it's time to ride. No start, after a good 60 pulls between me and my buddy. Ether/quickstart would get it going, but that's it, so we ascertained it was a fuel delivery/computer issue. Took off the dash, exhaust, and took off the fuel rail which sprayed some gas. Injectors looked fine, so we re-installed the injectors, and it starts after 2 pulls. Note: this season we pulled the power valves to inspect/clean them, as we weren't sure what the previous owner's maintenance was like, but they were in perfect condition.

Next year, same deal. Not until I removed the fuel rail, and re-installed it, will it then start after 2 pulls. No power valve work, as I only rode the sled maybe 600km the previous year.

This year, same crap; 75 pulls and it won't start on it's own. Remove the dash, another 15 pulls: no start. Remove the exhaust, another 15 pulls: no start. Disconnect the rail, and re-install it (spraying some gas). 2 pulls, runs perfect. Again no power valve cleaning, as I rode the sled maybe 50km last year.

So, I am thinking there's no way it's supposed to be like this "from the factory", so I am trying to figure out what's up, and make it so my fall checkup doesn't involve this seemingly pointless exercise. My current working theory is that, since the fuel rail isn't recirculating like it would be in a car, whatever fuel goes down that fuel line HAS to come out the injectors. Either:
A) The fuel in the line/rail will not burn after sitting for 7 months; when I disconnect the rail, I am basically draining the fuel line/rail of "old gas".
B) There is air getting into the fuel rail somehow, and the injectors are not opening until there is fuel in them, or they're burping air, but never enough for fuel to get there.

I do not use fuel stabilizer anymore; I figure it's not very long between when I stop using it, and when I give it a tune up, so it's not worth it. I did, however, put stabilizer the first year, and it didn't help. I fill the fuel tank before I store it at the end of the season, and I grease all the grease points, but that's it. I also use Arctic Cat APV.

Is there something I should be doing, that I am not doing? Is there a part that is worn-out somewhere that is causing this issue? It's annoying, and seems like there's no way this is the experience everyone has with this sled.
 

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Discussion Starter #3
No idea on compression, and no idea what the plugs look like; both seem to be irrelevant given the engine runs perfectly.
 

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When it won't start, do the plugs have spark? If they do and you are trying to start the engine and it won't start, pull the plugs and take a look. If they are dry, no fuel. If wet, too much fuel. Can you test the fuel pressure when you are trying to start it? Are you using fuel with ethanol in it? I hate that stuff.

What kind of oil are you using? On my 700, I was using one type of oil and when the sled would sit for a while, the engine would not start no matter how many pulls. I pulled the plugs and they were oil fouled. I changed to a different oil and have had no more issues. That's probably not your issue, but it is something you can check. Sometimes I had to add new plugs, too.

I'm not well versed on fuel injection, mine have run without issues over the years. I'm wondering if the pressure relief on the fuel rail is sticking and letting the fuel return back to the tank and when you remove the rail, it jiggles it enough to get it working again. That's totally a guess, though.
 

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OK have you drained out all the old fuel each year?
Fresh prem and Sea Foam?
Cat's EFI is about Bullet Proof, and even has a self diagnostic!
If there are no codes showing, then it is likely just maintenance!
 

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Discussion Starter #6
When it won't start, do the plugs have spark? If they do and you are trying to start the engine and it won't start, pull the plugs and take a look. If they are dry, no fuel. If wet, too much fuel. Can you test the fuel pressure when you are trying to start it? Are you using fuel with ethanol in it? I hate that stuff.
It has spark; runs with quick-start. I wish I had pulled the plugs; had I seen if the plugs were wet or dry, as you said, I would have known if ANY fuel was coming from the injectors (burnable, or not). Fuel pressure is good (I can't test how much pressure exactly, but it is "a lot". The fuel potentially has ethanol; I almost positively would have filled my sled from the gas station down the street, and Google says it is "up to 10% ethanol".
What kind of oil are you using? On my 700, I was using one type of oil and when the sled would sit for a while, the engine would not start no matter how many pulls. I pulled the plugs and they were oil fouled. I changed to a different oil and have had no more issues. That's probably not your issue, but it is something you can check. Sometimes I had to add new plugs, too.
Arctic Cat APV. Plugs don't seem to be an issue, since I change NOTHING except "burping the fuel rail" and it starts absolutely perfectly. I would have replaced the plugs if I had a set on hand; kicking myself for not having them available.
I'm not well versed on fuel injection, mine have run without issues over the years. I'm wondering if the pressure relief on the fuel rail is sticking and letting the fuel return back to the tank and when you remove the rail, it jiggles it enough to get it working again. That's totally a guess, though.
This machine does not have a fuel return; I believe this is the main issue, and is a very curious design choice, especially given the "not used every day" nature of snowmobiles.

OK have you drained out all the old fuel each year?
Fresh prem and Sea Foam?
Cat's EFI is about Bullet Proof, and even has a self diagnostic!
If there are no codes showing, then it is likely just maintenance!
My "end of year maintenance" involves using up the "old" gas (it would have been in the tank for maybe 2 months tops) as much as possible, then siphoning the rest for lawnmower use. I re-fill the tank with 91 octane from the gas station. I do not use sea-foam.

So, from those two comments, it looks like trying to avoid ethanol might be important, then sea-foaming the thing. Sea-foam doesn't seem like it would do much, but I am obviously not the authority on winterizing, so I suppose it can't hurt. The ethanol thing DOES seem like it might be an issue, so this coming spring, I'll make sure to get fuel that is ethanol free.

Unfortunate for me, I can't test anything anymore. I am not going to let it sit for more than a few weeks without starting it, because screw taking things apart again, so I'll only be able to re-test in the fall of next year.

I was really hoping someone would say "Yep, completely common on those sleds. Turns out you just have to blah blah blah blah and it resolves that issue". I have to get my fuel tank replaced for a recall, so it would be great if there is something I could do while the tank is off to resolve this.
 

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I have Polaris EFI sleds, and they start after sitting for months with 3-4 pulls of the rope. What you are experiencing is definitely not normal. On some sleds, if the fuel pressure regulator diaphragm gets stiff, it over-pressurizes the fuel rail, which can make the air/fuel too rich to burn. That will show on the plugs as being wet when starting. That's why it's important to get the specs for your system and check it with an accurate gauge. That's a pretty common problem on the older Cat EFI sleds, not sure on the newer ones.

EFI has a LOT of parts, and is a royal pain to troubleshoot when you are doing the work in your garage without all the tools and testing equipment the dealers have. Starting once a month may be your best option. Plus, you get to smell the two-stroke smoke during the summer :D
 

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Seriously Cat has it down.

Yes the Older style does give too much fuel and I have the fix for that.
If there are NO codes, and compression is 125, and plugs are fair, its fuel!
As I just told another, do everything.
Start with the new fuel tank!
Remove fuel pump and smart valves and clean them and go from there!
 

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Discussion Starter #9
I appreciate the input everyone, but what I don't get is that the ONLY thing I have to do to get the thing to start is lift the rail off the injectors, and put it back. After I do that, it starts. If the exhaust wasn't in the way, I'd be content with having to do that in the fall; removing/re-installing the rail is a 1 minute job, once the exhaust is out of the way.

Same 10% ethanol fuel, same fuel tank, same oil, same spark plugs, same computer, same compression, same air going in the engine, same idiot pulling the rope, same everything. Something is happening when the pressurized fuel-rail is removed and re-installed, and whatever is happening, that is the source of my issue.

A new theory is that the actual fuel line is potentially tainting the fuel IN THE ACTUAL LINE, and by removing the rail, it is draining that fuel line. Again, another theory, though I think I'd have pulled it enough times to have recycled the fuel in the line.


Also, re: "too much pressure": that is an interesting theory, but I'm curious how de-pressurizing the rail would resolve the issue.
 

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I doubt it’s tainted fuel in the line. Those injectors are pushing so much fuel it would push the small amount out in a sec not to mention the fuel rail being pressurized would mix old and new.

You don’t have a fuel pressure regulator on this machine? I would find that hard to believe most efi’s Have a fuel pressure regulator to dump the excess back to tank. It’s possible (if you have one, usually on the end of the fuel rail) it could be stuck open some. When taken rail off and on either you are knocking it around seating it or there is small vacuum leak on it and you reseat it allowing FPR to work correctly.
An in-line fuel pressure gauge would tell you that in a heartbeat.

On a side note why do you fill the tank up at season end and let the gas sit? Typically you want little fuel as possible to fill it later on during startup with new gas.

On EFI machines water is death to it. Ethonol atracts water. Bad and bad.
Sea Foam or Stabilizer would be a great choice for you if you continue to fill tank and leave it filled and sitting so long.
 

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Discussion Starter #11
I doubt it’s tainted fuel in the line. Those injectors are pushing so much fuel it would push the small amount out in a sec not to mention the fuel rail being pressurized would mix old and new.

You don’t have a fuel pressure regulator on this machine? I would find that hard to believe most efi’s Have a fuel pressure regulator to dump the excess back to tank. It’s possible (if you have one, usually on the end of the fuel rail) it could be stuck open some. When taken rail off and on either you are knocking it around seating it or there is small vacuum leak on it and you reseat it allowing FPR to work correctly.
An in-line fuel pressure gauge would tell you that in a heartbeat.

On a side note why do you fill the tank up at season end and let the gas sit? Typically you want little fuel as possible to fill it later on during startup with new gas.

On EFI machines water is death to it. Ethonol atracts water. Bad and bad.
Sea Foam or Stabilizer would be a great choice for you if you continue to fill tank and leave it filled and sitting so long.
There IS a fuel pressure regulator, but it's stupidly installed in the tank/with the fuel pump. But no, there is no return line ( IT IS CALLED RETURNLESS ); first time I've ever seen such a dumb setup. The fuel rail is basically a piece of square stock steel, with a tube at one end, and receivers for the tops of the injectors. An inline fuel pressure gauge, in my case, would just tell me "pressure is blah", which would be within specifications, given it currently runs perfectly.

I've done a bit more Googling, and many people have the same issue, though have not nailed it down to resolving it with my specific solution (basically, they were suggested to do a ton of things, but after removing the fuel rail, that seems to be the step where things eventually resolve themselves). It MIGHT be a fuel-pump issue due to poor engineering choices; apparently you can typically resolve this problem by just attaching the fuel pump to 12v, and not letting the sled try and power the fuel pump. It seems as though the omission of the return line is causing all of the types of problems the return line is intended to resolve, but running the pump just forces the problems out of the injectors quicker.

It does seem like the issue is actually air: the fuel sitting evaporates, or air is pulled in through here and there, and when the pump runs for 1/10th of a second, it gets the rail to pressure, but it's fighting a large column of air. However, since you're "burping" air from the injectors (which air is highly compressible, so the duty-cycle of the injectors would be removing very little of that air), you never (with my weak arms anyways) get to the point that fuel happens (at least, in the quantity required to start the sled). Pop off the rail, and fuel re-fills the fuel line, so when you re-connect, the system is now largely fuel, and it all runs.

Also, looking at the design, the top-half of the rail PROBABLY always has air in it, since there's no return line to deal with it. Basically, someone decided to save the weight of one rubber tube, and it's seemingly creating the problems that the return tube is designed to resolve. Maybe I'll install a bleeder valve on the rail, like most systems have, and just manually bleed off pressure in the fall.

As for stabilizer: it doesn't seem to help (since I previously had this issue even WITH stabilizer), but I suppose it doesn't hurt either. Ethanol might also be an issue, though I doubt it, but I'll make a point to try and avoid it this spring. Seafoam seems like it would also have no effect on anything to do with fuel delivery, seeing as how it deals with carbon deposits that were basically resolved in the 90s (took apart my Beretta 3100 with 395,000 MILES, and it was carbon-free), but once again … it probably can't hurt.
 

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Wow I agree that is a stupid setup. I would agree with you also on the air also in fuel line seeing how there is no purge on the end of the rail. If the rail gets air bound there is no where for it to go except the injectors.
Fuel injectors work off fuel pressure. To an extent anyways. This sounds crazy but as a fix you could have a shop drill and tap a bleed port into the end of the rail install a little bolt and oring. That why start of season you can crack it open and let sled turn over till you see fuel come out and tighten down. Assuming that is the issues.
 

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Wow OK
Again
Get the new fuel tank and clean the smart valves and the pump!
To clean the pump all you do is switch the polarity of the pump to spin it backwards!
 

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That's pretty wild. So this is only happening after the sled sits for a long period of time? No issues during the riding season?
 

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Discussion Starter #15
Wow I agree that is a stupid setup. I would agree with you also on the air also in fuel line seeing how there is no purge on the end of the rail. If the rail gets air bound there is no where for it to go except the injectors.
Fuel injectors work off fuel pressure. To an extent anyways. This sounds crazy but as a fix you could have a shop drill and tap a bleed port into the end of the rail install a little bolt and oring. That why start of season you can crack it open and let sled turn over till you see fuel come out and tighten down. Assuming that is the issues.
I was told the steel would very likely be too thin for the solution you proposed. However, A shop says they believe they can weld on some additional meat to that surface, and add a proper bleeder; virtually eliminate the chance of stripping it, and end up with a bit more robust solution that is less likely to leak.
Wow OK
Again
Get the new fuel tank and clean the smart valves and the pump!
To clean the pump all you do is switch the polarity of the pump to spin it backwards!
The sled ran, so cleaning the pump was not needed. In fact, generally speaking, spinning a motor "backwards", when it wasn't designed to do so, is pretty bad for the brush surfaces; while modern cheap motors are decent quality, putting any extra wear on them for no reason isn't the best. I hear reversing the motor IS a solution for stuck smart valves, but this wasn't my problem, so it wouldn't have fixed anything.
That's pretty wild. So this is only happening after the sled sits for a long period of time? No issues during the riding season?
I haven't started it since this post, but I did today: Pull 1 nothing (as per usual), pull 2 sputtering, pull 3 less sputtering, pull 4 less sputtering more "running almost" ... pull 8 started it.

So, confirmed that the sled sitting seems to add "air" to the sled's fuel system; 8 pulls of sputtering wouldn't "clean up" plugs, or warm up the cylinder significantly, etc, so it seems the issue that is clearing up is that fuel delivery is not significant, which would indicate something is coming out of the injectors that doesn't burn. Since I've now reasonably established it's a fuel thing, it does seem that sitting seems to add air to the fuel system somehow; either air is being drawn in through the injectors (potentially; this WOULD add air to the rail directly, and explain why not everyone has this issue), air being drawn in at one of the fuel hose junction points (which would basically have to be the rail one), or the fuel is "evaporating" (which would likely happen quicker in the summer). Whichever is the issue is largely irrelevant at this point, the fact is that there is "air" in there somehow is good knowledge.

I sent a pic of the rail to a friend, and he says he believes he can weld a bung to the rail (he was concerned it might appear to be made of some super-crappy material), and add a bleeder with no issue. I have a recall for my tank, which I can't get serviced any time soon (since the closest service location is like 3 hours away), but when they do it, I'm going to get them to replace that fuel line as well.

Once again, thanks everyone.
 

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Keep us posted. Maybe the dealer will have some insight. Have you tried giving them a call? Perhaps you could talk to one of the guys in service and explain things. They see a lot of sleds and a lot of different issues. Could always try calling multiple dealers as well.
 

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Discussion Starter #17
Keep us posted. Maybe the dealer will have some insight. Have you tried giving them a call? Perhaps you could talk to one of the guys in service and explain things. They see a lot of sleds and a lot of different issues. Could always try calling multiple dealers as well.
I contacted two dealerships, both had heard of this issue, but never found a resolution; good times.

I should be going to northern MI a few times in the winter, and those people are pretty active snowmobile service centers, so I am hoping for more information from them.

Thinking a bit more, I wonder if the o-ring @ the top of the injectors might be allowing air in; I don't see any gas bleeding down the injectors, but they weren't exactly perfectly clean when I got to it this fall, so I probably wouldn't have noticed. I've now cleaned up everything in the area, so if any fuel is going anywhere, I should be able to see it pretty easily.

Loose plan (at this time) is to go on a trip, and once I get to the first destination (so, probably an hour of beating on it), pop the hood and see if I can see fuel/oil anywhere near those injectors.

Thankfully it's not a huge deal, now that it's been running; I'll ride all winter without this causing any trouble, so if I can ascertain the root cause, I can fix it in the spring/summer/fall (or very late fall/winter, likely :) ).
 

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Discussion Starter #19
So, went on a trip to Grayling, MI, and just before heading up there, started the sled; took about 8 pulls, but it started. Ran it for a bit, did a onceover on lights, idlers, and such, and shut it down. Next day, tried to start it again to get it on the trailer, and the pull cord stayed out. Turns out, the cord got wet, and expanded, so when I pulled it, it was too thick to fit through the eyelet on the starter :). Easy fix, annoying that it happened.

As for THIS issue: I rode for about 300mi, and no oil/fuel seemed to be leaking anywhere, so there goes that idea :(. So, for this season, I'm just going to use it as it is; runs great as long as you've started it within a few days, so it's not impacting being able to enjoy the sled. I have a recall on my tank, so I'll get them to replace the fuel line while they're at it, and I'll see if I can source some o-rings for the tops of the injectors (which is still where I think the issue lies; heat is maybe masking the issue).

Maybe in the fall of next year, I'll know what the issue is :).
 

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Try this, just expose the wires to the pump.
Switch polarity on the pump Before you try.
Then pull it 3 times, the swap back and see if it starts second pull!

You could just have a sticky pump, and the reg is IN the pump!
 
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