How to Repair a Gas Trimmer That Won't Start

When a gas trimmer is working properly, a single pull of the starting cord is often enough to get it going. When it won't start, even after several pulls, you're either using the wrong starting procedure or the trimmer needs maintenance. The most common causes of poor starting are clogged filters, dirty spark plugs and stale fuel. The causes are related, and they produce starting problems most often after a long period of storage.

Check your owner's manual to make sure you're using the correct starting procedure. If your trimmer has a choke, the manufacturer usually recommends engaging it for a limited number of pulls -- usually three to seven. If the trimmer doesn't start, you usually have to turn the choke halfway or all the way off to prevent engine flooding. In addition, many units have priming bulbs; pressing the bulb the recommended number of times fills the carburetor with enough gasoline for ignition, but pressing it too many times can also flood the engine. Once the engine is flooded, it won't start until the fuel drains from the carburetor -- this can take 10 minutes or more.

If you're using the proper starting procedure and your trimmer still won't start, check the air filter. Remove the cover, using a screwdriver if necessary, and clean the air filter with soap and water or replace it. If your unit has a spark arrestor, you should also remove the arrestor screen and clean it with a toothbrush. Both of these filters prevent air from entering the combustion chamber when they're dirty. Inspect the spark plug next:

• Remove the plug with a spark plug wrench.

• Clean deposits off the electrodes with a file.

• Re-gap or replace the plug if it's corroded.

Starting problems after you have cleaned the filters and the spark plug are probably due to stale fuel or dirt in the carburetor or fuel lines. Dump out all the old fuel by turning the trimmer upside down over an approved container or, if you prefer, using a siphon tube. Check your manual for its location and replace the fuel filter, either by pulling the filter out of the gas tank or replacing the cap, which doubles as the fuel filter on some models. Fill the tank with fresh fuel, being sure to add oil in the proportion recommended by the manufacturer.

It may take several pulls to start a trimmer that has been contaminated by bad fuel. It sometimes helps to remove the spark plug again and pull the starting cord several times to force the bad fuel out of the carburetor and into the combustion chamber. Let the trimmer sit idle for about five minutes after doing this to allow the fuel to evaporate, and then replace the plug and try starting it. Starting fluid can also help get the trimmer going; remove the air filter, spray a one-second burst of fluid into the air intake and try starting the trimmer. If the engine turns over, it may smoke for a minute as it burns old fuel. Replace the air filter when the smoke stops.