.Chainsaw stumbles, quits

[metalman1]

People,

Have a Poulan 16" saw, recent tune up. Worked great for a few months (I hardly use it). Today, I started it up, started cutting 6"logs, ran great for 2-3 minutes, then started stumbling, coughing, and upon gentle throttle it coughed more, then quit. I waited about 1-2 minutes, and it started up with one pull, then started cuttting great for about another 30 seconds, then repeated the same problem. I checked the filter and it is basically still new. 

Should I mess with the low/high needles, turn clockwise/CCW?

Thanks, people.  

[beenthere]

Maybe crack the cap to see if starved for fuel when it starts to "cough".
Maybe dried fuel line that is the problem.
Could be a number of things, and wish you well finding the cause. 

Others will suggest other things to try. 

Just the name Poulan would be enough for me to be suspicious.  8)   Just kidding...

[metalman1]

Maybe crack the cap to see if starved for fuel when it starts to "cough".
Maybe dried fuel line that is the problem.
Could be a number of things, and wish you well finding the cause.

Others will suggest other things to try.

Just the name Poulan would be enough for me to be suspicious.  8)  Just kidding...

The loose cap idea is a good one. The high/low jets are probably fine as why else would it run great for 2-3 minutes.

[DHansen]

Resist the temptation to start messing with the carburetor adjustments.  Cracking the fuel cap is a good idea to see if the vent is plugged.  Check fuel and air filter to make sure they are clean. 

[KEC]

I'm not a saw mechanic by any measure, but I offered to tinker with a Poulan that someone had. I cleaned the saw, sharpened the chain, dumped out the fuel, cleaned the spark plug and put clean fresh non-ethanol fuel in it and it ran well. The fuel cap was REALLY hard to screw in/out. I bought a new cap and was told that the plastic that those caps are made of don't get along well with ethanol; makes the cap swell. Food for thought. Always start with the basic stuff.

[realzed]

Firstly - I would drain out all of the present fuel..  go buy a can of premixed fuel - let it sit in there for a while and then try and get it running again.  
If it does restart - get it rev'd up and going for as long as it will without a load on it at first - and if it stalls out repeat as often as necessary in hopes that the new and probably higher octane stuff will soften up and clean out any grunge that might have accumulated in the carb and fuel lines or flush it through..

[metalman1]

I'm not a saw mechanic by any measure, but I offered to tinker with a Poulan that someone had. I cleaned the saw, sharpened the chain, dumped out the fuel, cleaned the spark plug and put clean fresh non-ethanol fuel in it and it ran well. The fuel cap was REALLY hard to screw in/out. I bought a new cap and was told that the plastic that those caps are made of don't get along well with ethanol; makes the cap swell. Food for thought. Always start with the basic stuff.

Funny how my cap is swollen up too. I also think the vent hole has to be plugged up. I did unscrew the cap a bit until the fuel doesnt leak out, and plan on trying out the saw this weekend. I will let you guys know what happens. If it solved the problem I will not have to dump out the fuel like it was suggested. The fuel is fresh, by the way.

[KEC]

I hope your "fresh fuel" is non-ethanol. I will never again put a drop of ethanol fuel in any of my saws or other small motors, mowers, etc..

[Al_Smith]

I think what happens is the carb diaphragms get stiff from inactivity and ethanol in the gasoline .After a short run at high speed it just cannot supply the fuel and hiccups .You can tweek it ,make love to it change the fuel but the only thing that will fix it is to rebuild it .
You can travel all over the place and find nonethanol gasoline or spend 10 bucks a quart for something like VP fuel if it makes you feel better .I just rebuild the carbs if they fail .What I would like to know is why do so many people think rebuilding a carb is such a big deal  ???

[Tom King]

The best helper I've ever found for rebuilding a small equipment carb is a white dishpan.  Dollar stores almost always have them.  I keep a whole stack of them in the mechanic shop for organizing parts when I take something apart.

Keep all the parts in the dishpan, and they are easy to see and easy to find.

[mike dee]

Suck, squeeze, bang, blow.

Did you clean your filters? Not enough air will cause issues. Same with not enough exhaust.

Usually there is a metal screen spark filter in the exhaust. Sometimes it gets gunked up with carbon and un-burned 2-stroke mix. I pull mine apart and clean it with carburetor cleaner. Everything runs great after.

[Al_Smith]

More times clogged spark screens are caused by bar oil getting into the crankcase by some means .Depends on the saw design .It's not like mix oil because it won't burn up with the fuel .
Screens have a purpose like use in fire zones .However I don't live in a fire zone so very few of my saws have one .The hard wood woods in these parts it would take a napalm strike from a B52 to ignite .You could set fire to a wheat field though except why would anybody be in a wheat field with a chainsaw to begin with ? You normally use a combine for that task . ;D 

[fossil]

The later fuel lines have a liner in them (EPA) to stop fuel fumes from migrating through the line. The liner can turn to a snot like consistency mess.

You might check them.

[metalman1]

Finally got around to testing the chainsaw. The fuel filter (sponge) is clean. Again, I started it up, it cut great for about the same duration- a few minutes. Then it choked/spit/quit. Sheeeesh. Maybe it's time to take apart the carb, and look at the diaphragm. There is no such thing as ethanol free fuel around here. I used it since 1998. I am not convinced it is the blame. Maybe it is, maybe not. I have no choice, anyway. 

[metalman1]

Just dumped out all the gas and found brownish gunk in the tank. Can I flush tank out with clean gas, dump, and repeat? 

[DHansen]

You will get information from both sides of the fence on ethanol fuel use.  You can run it in small engines if you want to as long as it used correctly, and you understand the downfalls of fuels with ethanol or other alcohols added.   It is when it sets for a week of more that the problem slowly starts to happen.  So, in a gas can, in a fuel tank or float bowls of a carburetor.  The ethanol will separate from the fuel.  As this separation occurs the ethanol with drop to the bottom.  The ethanol will pull moisture from the fuel and/or surrounding air (atmosphere).  This will slowly start corrosion of metal and brass parts.  It will dry out and cause plastic to crack.  It will deteriorate the interior linings of some poor-quality fuel lines.  

[rusticretreater]

You will need something to agitate to clean or or a wand to physically break down any deposits.  You will need to replace the filter in your tank too.  Its a good time to check your fuel lines to make sure they are pliable and also examine to see if any contaminants have gotten into the fuel line and made it to the carb to mess that up too. :-\

[DHansen]

The corrosion and the deterioration then will lead to and cause the fuel system and carburetor circuits to plug up.  

[Ianab]

Probably want to replace the fuel filter, part of the pickup inside the tank, as well. If there was gunk in the tank, chances are it's now clogged up. Check the tank breather too. Cutting out after a couple of minutes may be because the vent isn't letting any air into the tank as the fuel drains. A quick test for that is when it dies, open the gas cap, close it again and see if it restarts and runs for a couple more minutes. 

[metalman1]

OK, that is a multi step process. Gotta do it. But wow, I also just found that the exhaust "box", was totally loose! How that happened, who knows. I dismantled it, inspected the screen, etc. Mounted it back securely. Could a loose exhaust box cause a bad engine performance, or is it just a quieting device? Aolso, that gunk turned out to be just brownish OLD tubing, all chopped up/cracked/deteriorated. Got it all out. I doubt it was the cause though, just sitting there......The shop that replaced the tubing many years ago must have not got it all out. 

Replacing tubing is a pain. Let me see how bad/hardened they are........

[DHansen]

You do not want ANY debris in your fuel tank or fuel supply.  Flush or fish all the deteriorated tube out.   I have seen fuel line tubing debris get inside of the new line and restrict fuel flow through the line.  It can also plug the fine inlet screen inside the carburetor that filters the fuel prior to the inlet needle and seat. 

[beenthere]

metalman1

There is no such thing as ethanol free fuel around here.

Where is "around here" ??

[metalman1]

metalman1

There is no such thing as ethanol free fuel around here.

Where is "around here" ??

Like, here, where I live. Central FL. In my neighborhood area, driving distance. 

[customsawyer]

Unless you update your profile there is no way for the rest of us to know that. It helps a lot when we are answering questions if you do fill it out. 

[btulloh]

I've heard that there's a bit of recreational boating in a few places in florida.  Is there a marina near you?  They usually have some corn-free gas.