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Thread: Stihl Chainsaw Won't Start

  1. #1
    Join Date
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    Stihl Chainsaw Won't Start

    My Stihl MS170 sat for years before now I need it. Fresh gas with Stabil pull and pull, nothing. Pull the plug, damp from gas replace plug, pull and pull nothing. Pull new plug lay on top, pull looks to be spark but not fat. Pull cover off, starting fluid into air intake to carb, nothing. Zero, thinking a weak spark ordered new coil and new Carb just in case. Since it would not start with Either I thought that was a clue. Comments?
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  2. #2
    You have spark, you sprayed in starting fluid, so somthing should have at least given you an indication of the issue. Does it even try to fire? Is the chain brake engaged? Have you checked for a clogged fuel filter (stabil or not)

  3. #3
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    I cant imagine you needing a new carb if youíve used it recently. Fuel issue?

  4. #4
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    One thing you can check is the coil gap. Too wide and the plug wonít fire under compression. Probably a YouTube video. I have a gauge but some use a dollar bill.

    Several things it could be. If coil gap is okay and it is firing the plug, I would do a pressure test, but you need a few things to be able to do that. Wonít pad pressure test, then you start looking for the leak.

    Just throwing parts at it is guesswork. Guesswork is as good as any only when you get lucky.

  5. #5
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    My experience with chainsaws is somewhat limited. One of my good running saw sat for a long year or more without being started the gas left a plastic like varnish around the diaphragm in the carburetor. I carefully cleaned it out and never left gas sit in the saw again.
    Good Luck
    Aj

  6. #6
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    Especially if it sat for a period of time with ethanol gas in it.

  7. #7
    Check for rust on magnets and coil assembly. Twenty bucks will get you a new magneto from Amazon
    Last edited by Bruce Wrenn; 02-13-2024 at 8:55 PM.

  8. #8
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    Why would you add anything to fresh gas? Check plug gap. for some reason some folks think they are factory gapped.
    BilL D

  9. #9
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    Stabil in everything, you fill the gas tank use it a couple times and then it sits.

    This chainsaw is my fault it set for 5-6 years. I checked the coil yesterday and the gap is good so I am not replacing it now, going to try to clean the carb. In case you folks have not noticed there are no idle or fast jets you can remove and clean and very little else thanks EPA. I have had good luck replacing the carbs with the ones from China so If I can not get it clean do to limited access I will replace.

    NO Ethanol ever in small engines at least I don't need to contend with that!
    Last edited by Bill George; 02-14-2024 at 9:14 AM.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  10. #10
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    Carb varnished up.
    NOW you tell me...

  11. #11
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    Bill

    Everytime I come up to a no start situation I try for 30 minutes then get on computer and replace everything. Its not worth the $20-40 in parts to fight it, just replace it. Your back will thank you.

  12. #12
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    My bet is on the carb putting it back to work now.

  13. #13
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    While youíre waiting for the carb to get there, pull the spark arrestee screen and see how clean it is.

  14. #14
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    Quote Originally Posted by George Yetka View Post
    Bill

    Everytime I come up to a no start situation I try for 30 minutes then get on computer and replace everything. Its not worth the $20-40 in parts to fight it, just replace it. Your back will thank you.
    Yep. New carb still in the Amazon package waiting for me to install it. That's when I'll find out if the -1 version of the carb was the right one or I should have ordered -2, -3, or -4. No clue in the listing - they all fit this model - and I haven't taken it apart yet.

  15. #15
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    An old Canadian neighbor taught me a trick. He gave me an old igniter coil from a furnace. He wired up a plug on the wires so it could be plugged in and create an arc. The trick is, BEFORE plugging it in, to put the spark pug on one of the terminals and a screw driver touching the base of the plug to the other terminal. Be very careful. Plug it in and let the plug arc for 5 minutes or so. It'll burn off any bad gas. After unplugging it the plug will be very hot but you'll be able to reuse it.

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