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String Trimmer Won't Start

The string trimmersmall engine often has a separate model number. Use the small engine model number for a complete list of symptoms and parts. Watch our model # lookup video for help finding the model number.

The part(s) or condition(s) listed below for the symptom String trimmer won't start are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.

Most Frequent Causes for String trimmer won't start

For the most accurate results, enter your model number.


Cause 1Spark Plug

Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.

Parts
Cause 2Carburetor

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Parts
Cause 3Carburetor Repair Kit

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.

Parts
Cause 4Rewind Spring

When the starter rope is pulled and released, the rewind spring recoils the starter rope onto the rewind pulley. If the rewind spring is broken, the rope won’t be able to recoil onto the pulley. As a result, the engine won’t start. If the rewind spring is broken, replace it. Many rewind springs can be replaced individually, but it may be easier to replace the whole recoil starter assembly.

Parts
Cause 5Rewind Pulley and Spring

The rewind spring might be broken. When the starter rope is pulled and released, the rewind spring recoils the starter rope onto the rewind pulley. If the rewind spring is broken, the rope won’t be able to recoil onto the pulley. As a result, the engine won’t start. If the rewind spring is broken, replace it. Many rewind springs can be replaced individually, but it may be easier to replace the whole rewind pulley and spring assembly.

Parts
Cause 6Recoil Starter

The recoil starter assembly engages the crankshaft to turn over the engine. If the recoil starter assembly is defective, the engine won't start. Remove the starter assembly and inspect it to determine if it is working properly. When you pull the starter rope, tabs extending from the pulley and cam should grab the hub on the engine, causing the engine to turn. When you release the rope, the tabs should retract and the rope should rewind back on the pulley. If the recoil starter assembly is not working properly, replace it.

Parts
Cause 7Recoil Starter Pulley

The recoil starter pulley winds up the starter rope when the rope is not in use. If the recoil pulley is broken or stuck, it won't be able to rewind the starter rope. As a result, the engine won't start. If the recoil starter pulley is broken, replace it.

Parts
Cause 8Fuel Filter

The fuel filter might be clogged. A clogged fuel filter is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the fuel filter and prevent the engine from starting. If old fuel was left in the string trimmer, drain the old fuel from the fuel tank and replace the fuel filter.

Parts
Cause 9Spark Arrestor

The spark arrestor is a small screen that prevents the engine from emitting sparks. Over time, the spark arrestor can become clogged with soot. If the spark arrestor is clogged, the engine may not start. To unclog the spark arrestor, remove it and clean it with a wire brush. You may also replace the spark arrestor.

Parts
Cause 10Air Filter

The air filter may be clogged. If the air filter is clogged, the engine will get too much fuel and not enough air. As a result, the engine may not start. If the air filter is clogged, replace it.

Parts