I've replaced the gas cap, and rubber grommet in the gas tank when I replaced the fuel lines.
I don't have a compression tester, but given it's a 2009 I suppose the engine could be shot.
The gaskets in the carb are new so I'd hope they're not leaking. There's one gasket right under the air...
Trimmer (John Deere T105C - 2009) didn't start at all, so I cleaned the old carb, no luck. I replaced
carb
spark plug (tested, it sparks)
fuel filter
fuel lines
air filter
I adjusted the throttle cable because it was loose, (worked, but was loose)
Now it runs great if I spray carb cleaner in...