One of the most common mechanical problems with push lawnmowers comes when the hand pull that is used to start the engine becomes stuck. This problem is usually more of a nuisance than a serious mechanical project or expense. A few simple techniques can be used to fix the most common pull cord problems and allow you to start the mower's engine. However, if the problem occurs repeatedly or cannot be remedied by these techniques, the pull string may need to be replaced.
Check to see if the mower's blade is bent. Bent blades sometimes cause newer mowers to lock up and not start. If a blade looks bent or crooked, replace it with a new blade. Simply unfasten the old blade with a wrench and attach the new one tightly. If the blade is new or straight and the hand pull fails to start the mower, the problem may be the string.
Spray lubricant on the hand pull string near the motor area and slowly pull on it. This will help distribute the lubricant all the way down the cord and even out any kinks. Repeat until the cord loses slack. Also make sure no debris such as small rocks block the cord from entering the motor cage.
Loosen the bolts on top of the motor carriage with a wrench. This is the area where the start of the cord is located. Pull on the rope to move it until it becomes loose on the track. This is a hard to reach area, so it may be difficult to reach the end of the rope on the first try. Tighten the carriage top back on with the wrench.
Pull on the rope again. If the cord still fails to retract properly and start the mower, the string may need to be replaced. Replace the string yourself or take the mower to a repair shop for a trained professional to do the job.