15 year old echo string trimmer Bulb will not

SOURCE: primer bulb on weedeater won't prime

when you prime the bulb it sucks gas from the tank with the small tube, any excess gassed pumped will be fed back to the carb via the big tube leading to the tank. If you prime it and the bulb stays pushed down, then you have a clog or kink. To fix , pull the small tube out of the tank through the fill hole. Pull off the filter on the end and put the tube back in the tank. If it primes, your fuel filter was clogged. If it still wont prime check the hose going to the carb and make sure isnt clogged or kinked.(take of carb and blow in it). If that doesnt fix it take off the bulb from the carb with two screws. The bulb assembly will come off too(rectange metal thing) Take off the two black gaskets, be carefull with them. Take off hoses from carb and bulb asembly. Blow carb cleaner in all holes and over surface. Put back together.
If the carb wont prime and the bulb isnt staying depressed. then you might have a bad bulb or carb gaskets. Make sure hoses are not cracked, cloged, or pinched.