Primer Bulb Mcculloch I Have A HomeLite Gas Trimmer.When I Press The Primer Bulb It Doesn't Come Back Up. What Causes This?

I have a HomeLite gas trimmer.When I press the primer bulb it doesn't come back up. What causes this? - primer bulb mcculloch

http://www.homelite.com/how_to/str_trim_zs.htm

This page shows exactly what I do, but the engine will not start because the primer will not return once pressed. I tried a new beginning and did the same. I also have a new fresh mix of 2-cycle oil and gas, and still nothing.