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bdawg8569

Craftsman 18' 42cc chainsaw won't start but has spark

bdawg8569
13 years ago

Hi everyone,

I am seeking some help with a craftsman chainsaw. I don't know what model it is. I haven't looked closely for it but it doesn't appear to be real obvious either. The saw came from an auction so i don't know the history of the unit. It wouldn't start when i got it home, so I began the diagnosis process. It has spark when the plug is taken out and grounded, however, I have not been able to get it to even pop off on starting fluid.

I found another post for a guy that said perhaps it was not sparking at the right time, possibly due to the fact that the key on the flywheel was sheered off. I took mine off tonight and everything looks great there. This saw looks like it was barely used.

They suggested that I take off the muffler as well and make sure the piston wasn't grooved from running too lean. As best i can tell it looks ok to me, though i'm not experienced with small engines. It has good compression, so i am at a loss as to why it wouldn't atleast fire up for a second with the starter fluid.

I would greatly appreciate any other ideas or possibilities that i could try. Thanks in advance,

Brian

Comments (25)

  • maryland_irisman
    13 years ago
    last modified: 9 years ago

    ..Take off the air cleaner, make sure the choke is NOT on.
    ..Set the trigger lock to high/start speed
    ..Remove the spark plug
    ..put about a teaspoon full of mixed fuel into the spark plug opening.
    ..quickly replace the plug
    ..pull the pull start and keep pulling until it pops. It may even run for 2 or 3 seconds.

    If it did give indications of starting, your problem points to fuel not being delivered by the carburetor. There are a number of reasons this can happen. Chain saws for homeowner use have a tendency to sit for long periods between uses. If fuel is left in there, it can turn to a shellac like sludgy substance and plug the various ports where fuel and air enter and mix. In the tank, the fuel line terminates at a small filter. It could be clogged with the sludge.

    If you are handy, remove the carb. and using the ether (starting fluid) soak the carb inside and out to clean the shellac off. Remove the the air/fuel mix screws and using the nozzle on the ether, spray it into the holes until it starts coming out from within the carb. Put the mixture screw(s) back in but be careful when tightening them. Once you feel it bottom out, turn the screw back out 2-1/2 turns. This will at least allow the engine to start and then you can fine tune the fuel mixture once it's running.

    Another problem with the fuel sitting in the carb for any length of time, is some of the newer fuel mixture. If you are using a fuel that uses ethanol, it will cause the aluminum to corrode and pit. It is also recommended to use 89 0r higher octane. If the saw had NOT been using ethanol gasoline, over time a shellac coating forms. Using the ethanol gas, starts cleaning this coating off the carb and serves to clog the ports. That is basically what is in those carb/fuel injector cleaners, along with a little naphthalene (lighter fluid). Ask anyone who has a motorcycle that never used ethanol gas and then used some!!!! It takes forever to work it out and in most case, the carbs have to be removed and disassembled and the ports unplugged. The same can happen to fuel injectors on your car although, consistently using the ethanol fuel or fuel injector cleaner, and running about 250-300 miles at interstate speeds will usually solve THAT problem.

    If your saw has a primer bulb, make sure it is not cracked or otherwise leaking. If it is, replace it. You must have the bulb on the saw for it to run, it acts as a float bowel. Also make sure there are no cracks or kinks in the fuel line.

    Once the saw gets running and warms up, let it idle and adjust the LOW mixture screw until you get the smoothest run. The idle speed screw is another you need to adjust. Adjust the idle speed at a speed where the saw chain does not move. Then, squeeze the trigger a bit and moving the HIGH mixture screw in or out, a little at a time, adjust until you get the smoothest run. Be careful at the higher speed since the centrifugal clutch will engage and the saw blade will begin moving requiring you to hold the saw in place more forcefully.

    When checking the spark plug, was the spark yellow or blue? If it was yellow, there is too much resistance to the plug or, the spark needs to be adjusted. If it was a blueish spark, that is generally a good spark. If the above gets things going for you, I suggest replacing the plug. They are CHEAP, LESS THAN 5 BUCKS.

    As with any engine, don't leave fuel sitting untreated for more than 3 months. Follow the directions on the label of a product such as STABLE. You'll notice now days, it has a blurb stating a new formula for ethanol fuels. Even though they claim you can leave it in there for a year, I wouldn't do that. On your saw, allow the saw to run empty until it stops.

    Be sure to use fresh gasoline and the correct fuel/oil mixture on your saw.

  • bdawg8569
    Original Author
    13 years ago
    last modified: 9 years ago

    Thanks for taking the time to post. As I mentioned in my first post, i was unable to get the saw to even pop with starting fluid. I tried your suggestions, but to no avail, tho not surprisingly cause the starting fluid was the same test. I did find out that the model of the saw is 358.350480. I was unsure what you meant about setting the trigger lock to high/start speed. I assume that you thought maybe this model had a trigger lock for the throttle? I realize you didn't know the model at the time of writing but there isn't a throttle lock on this one, or maybe i'm misinterpreting what i was supposed to do. I found a manual online and didn't see anything about trigger locking.

    Your information about the carb or fuel system being the problem was right on, that is why i had begun testing with starting fluid in the beginning. I am just puzzled as to why the engine would not atleast pop off since it has good compression and good blue spark. I am baffled here. I am no small engines expert by any means, but i have had good luck working on a few weed eaters, but this one really has me stumped. Any other ideas i can try anybody?

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  • handymac
    13 years ago
    last modified: 9 years ago

    How are you testing the compression? Resistance to pulling the starter rope is not a reliable compression test.

    You said the cylinder/piston looked good---were there any marks in the cylinder or on the piston? Any lines/gouges in the cylinder/on the piston is a sign of a problem. A good cylinder is shiny like a mirror.

    Try starting the saw with the muffler off. Just do not run it more than a second or two. Completely plugged muffler(bad baffle) can give you a no start.

    The only other things I can think of is the coil pack is out of time or the spark plug is defective. I have seen plugs that will show spark out of the engine, but not under compression.

  • bdawg8569
    Original Author
    13 years ago
    last modified: 9 years ago

    Handymac,
    Thanks for the advice. I think it was one of your posts from another thread that got me started doing the things i have done thus far. Resistance to pulling the starter rope and just putting my thumb over the carb hole is the only way i have tested compression. Is there some other way i can test? I said that i think the cylinder/piston looked good. I didn't see anything but it is a small window to see through and it was kind of hard to tell. I have replaced the spark plug, so i have tried starting it with 2 plugs both of which have had spark. I tried taking off the flywheel to make sure the key was not sheered off and it was fine too. I will try starting it w/o the muffler tonight when i get home. I appreciate all the advice. So the saw wouldn't even pop off for a second if the piston or cylinder has marks on it? Thanks in advance,

    Brian

  • maryland_irisman
    13 years ago
    last modified: 9 years ago

    If you have spark, fuel and compression, you should at least get a pop, even if it were a backfire. I would do as suggested concerning the muffler. I would also check to make sure the carb is not plugged. Without air entering, you won't get a fire.

    Another thought would be the diaphragm in the carb, as far as fuel is concerned.

    Usually, when these type saws are dropped (or thrown in disgust) the magneto coil moves into the flywheel. Usually when that happens, you can't pull the cord. Maybe it went into the other direction and is too far from the flywheel which contains the magnet. If the spark is more yellow than blue, that is an indicator the coil is too far away and you are getting a weak spark. Slide a piece of paper folded to the thickness of a match book between the flywheel and the magneto. Loosen the magneto and slide it forward until it is firm against the paper and then tighten it back down. Pull the paper out and you should have about a .17 space. This will give you a good strong spark.

    I don't have anything in front of me so I need to ask if this unit has an electronic control module that takes the place of points and condenser. If so, you might want to look at that as a possible problem.

    Good luck!!! I'll be checking in to see if someone else has an idea or, if you would be so kind, let us know what happens.

  • handymac
    13 years ago
    last modified: 9 years ago

    Two cycle engines are renowned for being tempermental. I have had no starts that I disassembled, inspected tested parts, and found no deficiencies. Reassembled it and it fired right off.

    You said you bought the saw at an auction. There is a possibility there are some incorrect parts on the saw---like the flywheel. If the flywheel were incorrect, the magnet that triggers the coil which creates the spark at the plug could be firing the plug way out of time. Only takes about 5 degrees.

    I'm trying to imagine any oddball things---the flywheel idea is really odd.

    I had a compression guage for testing compression when I repaired saws.

    I just had a really whacked out thought. There are rings on the piston, right? Should be at least two. A lot of chain saw pistons are just a wee bit smaller than the cylinder bore and actually could be installed by a DITer without rings and 'seem' right. Definately would not fire, tho.

  • bdawg8569
    Original Author
    13 years ago
    last modified: 9 years ago

    Guys,
    I tried most everything discussed and the dang thing just will not even try to backfire or give a hint of starting. I don't know what to do. It makes a good paper weight, but thats about it. Perhaps something to shoot at with a shotgun. It's so frustrating. I guess I will have to take it to somebody that knows more about it than I do. I appreciate the help and wish I had better news, but unfortunately i don't.

  • Foreverwood
    11 years ago
    last modified: 9 years ago

    I repaired a chainsaw for a coworker and his had spark, but would not pop also. Turned out his saw was notorious for flooding and when i constantly pulled the cord on choke it was continuously flooding. One day I tried starting it wide open would no choke and it fired right up. It still has times that it does not pop and i told him to move it to half throttle and BAM it starts again. Don't know why its been happening, but it works well. Has your plug been getting wet?

  • Jim Jakosh
    7 years ago
    last modified: 7 years ago

    Hi Brian. I have an 18" 36cc Craftsman chain saw that will not even pop with Gumout in the cylinder. It has good spark and compression. I have not checked to see if the key is sheared but It is from the original owner and he is not hard on tools at all. . He had the carb rebuilt at Ace Hardware a year ago and they said they started it but he cannot get it going. I took it back to Ace and they could not get it going either. They said the one line was sucking air. I found both of the primer lines cut and while replacing them I found they were on backwards- blowing into the tank and sucking from the carb. I corrected that and put on new lines but the darn thing still won't pop. I called Sears hotline to see if there was a bulletin on it and they said no . If it has compression, spark and gas it should fire. I'm going to pull the flywheel to check the key. If that is okay, the next stop is the dumpster and buy a different brand.

  • Jim Jakosh
    7 years ago
    last modified: 7 years ago

    Well Brian. I pulled the flywheel off my chainsaw to look at the key and there is no loose key. It is built into the flywheel. so, if it would shear, you would have to buy a whole new flywheel.Brilliant engineering ( for those selling parts..not for the customer.) Mine was not sheared and the gap was .008" which is okay too. And it still does not start. The only thing left is that they have it timed off in the manufacturing of this saw. Since I am throwing it away anyway, I think I will enlarge the mounting holes for the coil so I can move it to change the timing. I just have to determine which way. It might need only a few thousandths ( like the amount if a key shears) to make a difference. In the mean time I'm writing to Sears engineering to explain this and see if they found the timing to be off on any of these. I'll keep you posted. This really bugs me!!!!!!!!!!!!!!!.............Cheers, Jim

  • klem1
    7 years ago

    If misery love's company perhaps this will make you feel better. I have a sears saw that started and ran fine until the primer bulb cracked. I replaced the bulb,it didn't start after priming,I gave it a shot of starting fluid and it has been dead since. I've began to think ether ruin's 2-cycle engines because looking back I've had others that never ran again after I used starting fluid. Maybe it blow's a seal inside engine but just like op,I was never able to get a puff of smoke much less attempt to start. I'm thinking of trying a propane saw or weed-eater to get past ethenol problems.

  • Jim Jakosh
    7 years ago

    Hi Klem,did you notice if the hoses on the priming bulb were in the right order. Mine had them reversed and I only found it by the screeching noise I heard. The hoses had cuts in them and the one that is supposed to suck the fuel, was hooked to the carb. Does your bulb fill up okay.

    As for starting,even if you had no carb on the engine and no gas hooked to it, if you put a bit of fuel in the chamber with compression and spark, it should pop and burn that bit of fuel, UNLESS the spark timing is off. It is similar to when you build an engine for your car and you install the distributor set on the right cylinder that is on the compression stroke, it will not fire until you turn the distributor enough to get the spark timed right. if you get it too far one way of the other, the engine will buck and not fire. I noticed something like that in my saw. I'll be cranking on it and then it will pull real hard, like maybe it is detonating the fuel early. It seems like that would happen coming up on compression so the spark may be too early. I don't want to let this one go now that I'm n the trail. I have asked Sears if they had that to be an issue where they manufacture them. It might just be the holes are a bit off that locate the coil. Cheers, Jim

  • Mike C
    6 years ago

    Magnet gone on the flywheel?

  • Cameron Ells
    6 years ago

    I checked that too. I also ajusted the distance between the flywheel and coil. I think it might be a bad coil.

  • kennedytom
    6 years ago

    My son had the same problems. His would start and run for 1/2 second and die. He tinkered with it half a day before he found the problem. It seems the fuel line from the carburetor to the fuel tank was messed up. The fuel line was removed and the line has a line inside the line with some wire in it to keep it from collapsing (I think). Anyway he went to the auto parts store, bought a new piece of fuel line and replaced the bad line. If you do this be sure to add the weight back on the fuel line inside the tank so the saw won't starve for fuel if you should turn it on its side.

  • brokenbeetle
    6 years ago

    I just went through a similar problem with my craftsman 18inch chainsaw. Loaned it to someone and when I got it back it wouldn't start. Went through all the steps mentioned already. Finally looked on YouTube and s found someone else having a similar problem. Turned off the choke, full throttle on the gas trigger, then it started up after a few pulls.

  • roivany
    6 years ago

    my Stihl 170 wont start. I replaced the fuel line, added a new carburetor, cleaned all parts thoroughly, checked all filters and still only goes for a second on the priming fluid. Totally frustrated - what else is there to do?

  • handymac
    6 years ago

    Remove the muffler and check the cylinder/piston for gouges/scratches. If the cylinder/piston are scratch/gouge free, the problem may be in the ignition/timing system. If there are deep scratches in the piston/cylinder, those are damaged and would have to be replaced. However, replacing the piston and cylinder head can be almost as expensive as buying a new saw.

  • HU-113090961
    4 years ago
    last modified: 4 years ago

    I'mhI'm having the same problem with my craftman 42cc chainsaw. Replaced all fuel lines,new carburetor ,purge ball ,spark plug and still nothing. Noticed it was extremely flooded. Everything replaced the way it was taken off. Filled fuel tank up when first started to get it to start now tank almost empty but chainsaw never ran.

  • Jim Jakosh
    4 years ago

    I scrapped mine............Too much time invested!

  • Carson Abboth
    4 years ago

    I never had problems with my Craftsman saw except only once, but it all ended up with a chain replacement. As said in this review Oregon 18" chain fits perfectly, by the way.

    But if saw requires fuel line or spark plug replacement, it's just a waste of money in my opinion.

  • HU-503104992
    2 years ago

    This thread is insane but full of great information.. very informative. But my craftsman 42cc still wont pop. All testing and maintenance done.

  • Stetson Reece
    last year

    Hey guys, I'm Stetson. I got a 16"(originally) Craftsman S160 (42cc) and I've tried everything on this page. I've bought a new carburetor and ignition coil and put them on but still nothing. It's got a good blue spark and the right mixture of gas, which is 40:1 on this model, and I've looked at everything times over but I did find out tonight after the 500th disassembly that one of the piston rings was missing and the other was damaged. I've ordered replacement piston rings. But am just wanting to make sure, the missing piston ring IS the reason why it isn't starting, right?

  • Dave Ovington
    last year

    Craftsman 42cc, I can get it to start for a minute and then when I hit the throttle it bogs out. I've been through the jet setting all the way from open to close and back again. I've cleaned up and checked the saw over front to back and I can't find anything wrong. Did see someone suggest that the timing could be off so I'm going to try that I .any ideas would be great