Move the trimmer On/Off switch to the "On" position.
Check the fuel tank to make sure the fuel level is near the full line indicator. Add fuel if necessary.
Check the spark plug for cracks and replace if necessary. Pull the spark plug wire off with your fingers. Remove the spark plug with a socket wrench. Install the new spark plug and tighten with a socket wrench. Push the spark plug wire on with your fingers.
Check the fuel line for cracks. Replace the fuel line if necessary.
Check the fuel to determine if it is old or mixed incorrectly. Place a drain pan under the fuel tank. Remove the fuel cap and tilt the trimmer slightly to allow the old fuel to drain into the pan. Add new fuel and replace the fuel cap. Dispose of the old fuel according to local regulations.