A good string-line trimmer will last for years with proper upkeep and regular maintenance. When something does go wrong, however, it is helpful to know what can be done to fix the problem. Some trimmer issues are easily repaired at home, while others may require help from a service technician. Whether you choose to complete a repair yourself or take it to a professional, you will probably end up working with a service department. If you are not comfortable diagnosing and repairing your trimmer's problem, or if you simply don't have the time, trained service technicians will be able to correct the issue. On the other hand, if you want to do the repairs and maintenance yourself, a competent service department can help you locate the correct replacement parts and provide advice for completing repairs.

Basic Troubleshooting

When your trimmer won't start, the first thing you should check is the fuel. Letting fuel sit in an engine for too long, usually about 30 days, can make the fuel go bad. If the trimmer has been sitting idle with fuel in it, drain the tank and refill it with the proper fuel/oil mixture. To prevent this problem in the future, you can add a fuel stabilizer. If the fuel is good, check the spark plug next. If the spark plug is corroded or damaged in any way, it should be replaced. Spark plugs are relatively inexpensive and easy to change, so this problem should be one that you can take care of with little inconvenience. Another thing you can check if the trimmer is having trouble starting is the air filter. Air filters are located on top of the engine's carburetor and held in place by a cover, which is usually easy to remove. Foam filters can be washed with detergent and water, or replaced if they are badly damaged. Paper filters will typically need to be replaced.

Checking the Engine

For two cycle engines, which use fuel mixed with oil, one of the most common problems is a clogged spark arrestor screen. The oil in the fuel is not usually burned off completely, and can carbonize on the screen. Often an engine with a carbonized spark arrestor screen will start, but not rev up. To clean the screen, remove the muffler cover and brush the screen with a wire brush or burn the oil and carbon out with a torch. More serious problems with a string line trimmer can be difficult for a home mechanic to identify. If cleaning or changing the spark plug, filters, and spark arrestor screen does not solve the problem with the trimmer, it might be time to take the trimmer to a service department.