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Stihl 026 runs only with choke on

Discussion in 'Chainsaw' started by d-rose, Jan 26, 2011.

  1. d-rose

    d-rose ArboristSite Lurker

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    I have an 026 that only runs with the choke engaged. I had noticed it starting to run inconstantly the last couple times I used it. A little adjustment on the screws and it would take off. I'd zero everything out and put a turn in the H & L. Now it only runs with the choke on. Evidently starving for fuel. Checked the fuel filter and fuel line. They check out good. No holes in the line. I'm suspecting seals. Started to do a vacuum test last weekend but my vacuum pump is hosed. Gaskets and seals are cheap....$10. Am I looking in the right direction? Thanks in advance for any comments.
     
  2. Brian VT

    Brian VT Addicted to ArboristSite

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    Check the impulse line.
     
  3. Brian VT

    Brian VT Addicted to ArboristSite

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    ...and fuel tank vent.
     
  4. Brian VT

    Brian VT Addicted to ArboristSite

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    ...and intake boot/clamp.
     
  5. d-rose

    d-rose ArboristSite Lurker

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    Thanks Brian. I thought about the vent. But, wasn't sure how to check it. I turned the saw over on it's side and there was gas that seeped to the outside of the filter. So, I assumed it was good. Would it be? I didn't take the intake off, but did pull the carb and the rubber of the intake seemed soft. I assume it is good. ran the same after replacing the carb. Now, the pulse line, I was time constrained and probably a bit lazy. But did not disassemble far enough to take it off and check. I will check these three again. Like I said before, my vacuum pump is bad. I do have a gauge. Could the gauge attached to the impulse line show that it is good or bad when cranking the saw? Or do I need to take the saw down far enough to take it off and check. I have a parts break out but no service manual. I think I go begging for a manual so I can read a little and not hack so much.
    Doug
     
  6. Brian VT

    Brian VT Addicted to ArboristSite

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    Check to make sure it's attached well at both ends and that it's not dried out and/or cracked. I doubt it puts out enough psi to move a gauge.
    I would replace it anyway, but that's jmho.
     
  7. smilin possum

    smilin possum Addicted to ArboristSite

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    May have trash in the carb to. If you have to run it with the choke on it's a fuel problem or some of the lines have a pin hole.
     
  8. Great Smokies

    Great Smokies ArboristSite Operative

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    To me, this is totally a carb issue. Your screen is plugged or the diaphragms are getting hard- it isnt getting enough fuel. Quick test- with the saw cold, shake it to agitate the gas, pull of the fuel line from the carb. If its spitting fuel, then fuel is getting to the carb, but not through it. If it was the impulse, it wouldn't be pumping at all, but it must as it does run, just not right. If it was air leaking it would be running high, not idling down due to running lean. So, rebuild the carb, and that should be it.
     
  9. JoshF

    JoshF ArboristSite Member

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    The impulse is strong enough to move a gauge if it shows pressure and vacuum. At least on all the saws ive tried it on
     
  10. d-rose

    d-rose ArboristSite Lurker

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    Sorry, I went back and read my post. I failed to mention that when it is running with the choke, it runs very fast. It won't idle down. As soon as I shut the choke off, it dies in less than a second. I'll check all that has been mentioned. I really appreciate everybody's input. 2 strokes are new to me. Got my first experience last fall rebuilding my dad's golf cart engine.
     
  11. CTYank

    CTYank Peripatetic Sawyer

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    Sure sounds like air-leak, at carb to case boot, or (less likely) crank seals.

    Of course, you could have changed the idle speed adjustment without us seeing it. :secret:

    Not knowing the history of the engine/carb, I'd rebuild it first, while waiting on whatever it takes to do vacuum/pressure test.
     
  12. Brian VT

    Brian VT Addicted to ArboristSite

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    It's getting too much air for the amount of gas it's getting, so it won't run.
    When you choke it, you're letting much less air in and getting the air/fuel mixture close enough that it will run, but it's still lean (too much air).
    You either have air coming in from somewhere it's not supposed to be or you're not getting enough fuel to the engine. All of the suggestions given are possible solutions.
     
  13. d-rose

    d-rose ArboristSite Lurker

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    ok. Problem finally solved. After replacing the fuel line, I cleaned the carb again. Don't know how I missed it before, but the screen in the carb was full of crud. Thought I'd checked it before. evidently I didn't. Started on the third pull. Man, don't I feel dumb. Anyways... Thanks to all who piped in and gave some guidance.
     
  14. a. palmer jr.

    a. palmer jr. Addicted to ArboristSite

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    Any time an engine runs only on choke the first place I check is the carb. I usually go ahead and rebuild because it's rather inexpensive and easy.
     
  15. huskydave

    huskydave Addicted to ArboristSite

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    I would have to agree. would pull the carb and rebuild it. You can inspect the carbboot and impulse line while your at it. You could change out the fuel filter as well.
     

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