Weed wackers won't start

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  #1  
Old 07-17-07, 08:05 AM
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Weed wackers won't start

We have one used Sears weed wacker that had ran great for a few years and now it won't start at all. We also have a second Sears weed wacker which is fairly new and it won't start either, the newer one ran for a few days and ran great but now it has problems. I have changed out the spark plugs, new fuel with 40:1 mix ratio, cleaned the air filter, cleaned the needle valve and port, cleaned the spark timming magnets and pick up's etc. I have tried everything and they still won't start. any ideas? any suggestions would be greatly appreciated.
 
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Old 07-17-07, 01:57 PM
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you need air/fuel, compression, and spark for an engine to run.

Test the spark by taking out the plug and holding it against the top of the cylinder. then pull the starter cord and look for sparking at the end of the plug.

If you have a compression tester, to a compression check, if the engine is still good you should have at least 90psi. If you dont have a compression tester, cover the spark plug hole with one of your fingers, pull the starter, and make sure it is forcing air out past your finger.

You said you cleaned the needle valve. So I'm guessing you also inspected the diagphram and it was in good condition.

After you try starting the trimmer, take out the plug and inspect it, what is it like? Is it wet with a gas/oil mixture?
 
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Old 07-17-07, 06:30 PM
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Don't overlook the fourth element needed...exhaust. If you have a plugged muffler or muffler spark arrestor screen the exhaust gases can't escape and the engine can not run.
 
  #4  
Old 07-17-07, 06:45 PM
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tested

Originally Posted by zzzz1486 View Post
you need air/fuel, compression, and spark for an engine to run.

Test the spark by taking out the plug and holding it against the top of the cylinder. then pull the starter cord and look for sparking at the end of the plug.

If you have a compression tester, to a compression check, if the engine is still good you should have at least 90psi. If you dont have a compression tester, cover the spark plug hole with one of your fingers, pull the starter, and make sure it is forcing air out past your finger.

You said you cleaned the needle valve. So I'm guessing you also inspected the diagphram and it was in good condition.

After you try starting the trimmer, take out the plug and inspect it, what is it like? Is it wet with a gas/oil mixture?
It has great compression, I'll double check the spark like you had suggested using the spark plug and pulling the start cord. Thanks for the suggestions and help.
 
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