Small Engines (Lawn Mowers, etc.): Echo string trimmer, echo string trimmer, long nipple

Question
I have a CS-306 string trimmer model serial # 02008118.  I have replaced both diaphragms and gaskets, and blew out all the holes in the carb with air.  I did not replace the needle valve.  The tube from gas tank to carb is clear and I cleaned the filter.
When I push the primer bulb, it will not fill with gas.  I put in a new bulb and it still doesn't work.  I can start with starter fluid, but it will not keep running.

Any help will be greatly appreciated.

Answer
Is this a Chainsaw?  Do you have a Walbro WT-589 carburetor?  Did you mark the primer bulb fuel line connections before you replaced the primer bulb?  There should have been a short and long nipple on the primer bulb.

Since you did not replace the needle it may be sticking.  Do you have a pressure tester to check the inlet needle pop-off-pressure?

Eric