lawn mower starter lost tension, after pull cord replaced, cord problem, metal spring, or metal cluth problems
broken cord at the pulley, [over strenth pulling caused], replace it back into position, now, little tension after rewound back, but after pull it out with little tension, starter did not do anyting, and the cord lost tension completely. 
thanks for your help.
usually this means that either the clutch has siezed. Sometimes you can remove the top cover and spray the insides with WD40 to free it up.
If not, try a local small engine repair shop before you go to one of the bigger garden centers. The local shops tend to be a little cheaper and give better quality service.
