How to Start a Stubborn Weed Trimmer With a Thimble and Some Gas

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Weed trimmers can be a pain to start at times, and when they start to get old, sometimes they need a little help to get some gas into the cylinder head. Some use starting fluid for this, but a small amount of gas can work as well, as explained in this article.

  1. How.com.vn English: Step 1 Make sure the gas tank on the trimmer is full before assuming it's not working properly.
    Do a quick check to satisfy yourself.[1]
  2. How.com.vn English: Step 2 Take off the...
    Take off the spark plug with a spark plug wrench.
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  3. How.com.vn English: Step 3 Check the rim below the point of the spark plug for build-up of carbon deposits, and the point as well.
    The rim should be silver and not black, and the point should not have build-up on it either. If the rim needs to be cleaned, scrape off the deposits with steel wool or a use small flat head screwdriver. Be careful not to break the white ceramic insulator.[2]
  4. How.com.vn English: Step 4 Make sure you are well clear of any gas and then heat the spark plug rim with a butane lighter.
  5. How.com.vn English: Step 5 Fill up a thimble with gas and put into the chamber, then put spark plug back on and tighten it on.
  6. How.com.vn English: Step 6 Put on the choke, prime three times, waiting 4 seconds between each prime.
  7. How.com.vn English: Step 7 Pull on the starter rope a couple of times until you hear the engine begin.
    It should rev up a little then stop because choke is still on.
  8. How.com.vn English: Step 8 Pull the rope again with choke off a few times and the engine should start.
    • If the engine does not start, replace the spark plug with a new one, as this could be the problem. (The old spark plug has a number on it, so write it down before going to the store).
  9. How.com.vn English: Step 9 If it still...
    If it still does not start, it could be the carb is gunked with deposits, in which you will need at this point, some carb cleaner.[3]
  10. How.com.vn English: Step 10 Clean the carb.
    To clean the carb, remove the carb cover and spray off the jets, making sure that they are clean and unobstructed.[4]
    • Then take off the primer cap from the line and spray carb cleaner down the tube where the cap was attached and replace the primer.
    • Press a few times, forcing the carb cleaner in the line into the carb.
    • Repeat this process a few times.
  11. How.com.vn English: Step 11 Check the spark arrestor screen, which can also be clogged.
    This is a screen that prevents hot particles from escaping the muffler, which can cause a fire. If it is blocked, remove it and scrape with a wire brush or a piece of wood, then replace it.[5]
  12. How.com.vn English: Step 12 If the trimmer still does not start, it could be clogged, and may need a new carb.
    Also note whether after you have put a few drops of gas in the cylinder, and replaced the spark plug, it fires up for a little but does not run. If so, this could mean the carb is blocked, because gas is not getting from the carb to the cylinder, and the only thing that's making it run for a bit, is the little gas you put in the cylinder. If it does not run at all, it is usually because the spark plug is either spent or dirty.
  13. How.com.vn English: Step 13 Always empty all the gas out of the trimmer and all gas-powered equipment at the season's end.
    Press primer bulb a few times forcing excess gas in line to run into carb, and then pull starter rope a few times forcing all the gas out. Excess gas sitting in the line and in carb over the winter causes blockage, so always empty and clean when not in use for extended periods.
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Community Q&A

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  • Question
    What can cause the trimmer to stall after pulling the trigger?
    How.com.vn English: Community Answer
    Community Answer
    Bad air/fuel mixture. Dirty gas, often water in carb. Clogged muffler screen. Clogged air filter. Spool head could be binding from long weeds wrapped around.
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      Tips

      • Today's ethanol gasoline is a big problem for small engines, two-stroke and four-stroke, especially engines that are not used every day or two. Ethanol will separate and go to the bottom of the tank. It will also leave a gummy residue or "varnish" on carburetor parts and ports. Some say this is the cause of most small engine problems today. These small carburetors have small ports, needle jets, screen filters, and holes that can be blocked or partially blocked by the smallest impurities.
      • Replace the weighted filter in the gas tank on weed trimmers. These filters are easy to remove with a small hook on the end of a "coat hanger" wire. The weighted filter is on a length of tubing in the gas tank and allowed to reach the bottom of the tank no matter how you hold the trimmer. The filter can easily become clogged with all kinds of debris.
      • To prevent this problem in your engines, use a gasoline additive in every gas can before you fill any small engine gas tanks. Some additives will prevent the problems; some will help remove the varnish and gum. These additives are inexpensive and cheap insurance.
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      Warnings

      • Don't try this if the engine has been running and hot. If you spill gas, it could ignite if it contacts the hot engine.
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      Things You'll Need

      • Spark Plug Wrench
      • Trimmer
      • Thimble
      • Butane Lighter
      • Gas

      About This Article

      How.com.vn English: Ben Barkan
      Reviewed by:
      Garden & Landscape Designer
      This article was reviewed by Ben Barkan. Ben Barkan is a Garden and Landscape Designer and the Owner and Founder of HomeHarvest LLC, an edible landscapes and construction business based in Boston, Massachusetts. Ben has over 12 years of experience working with organic gardening and specializes in designing and building beautiful landscapes with custom construction and creative plant integration. He is a Certified Permaculture Designer, is licensed Construction Supervisor in Massachusetts, and is a Licensed Home Improvement Contractor. He holds an associates degree in Sustainable Agriculture from the University of Massachusetts Amherst. This article has been viewed 216,594 times.
      How helpful is this?
      Co-authors: 12
      Updated: April 29, 2024
      Views: 216,594
      Thanks to all authors for creating a page that has been read 216,594 times.

      Reader Success Stories

      • How.com.vn English: Kevin Noy

        Kevin Noy

        Jun 21, 2020

        "Good info. I forgot a couple of steps to make it happen, but this hit my memory button. Thank you."
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