A weed eater can keep dying because of fuel or air delivery issues which can be a result of clogged carburetor, clogged main jet in carburetor, dirty air filter, fuel cap issues, or even bad fuel lines or clogged fuel filter inside the tank of the weed eater.
A clogged carburetor, which is often caused by old fuel or debris, can restrict the flow of fuel and cause the weed eater engine to stall or cut out when revved.
A clogged fuel filter and even a blocked fuel cap vent or clogged or cracked fuel lines can cause your weed eater to cut out when revved or cut out any other time as well.
When the air filter is dirty it restricts the airflow, which leads to a rich fuel mixture and stalling.
A clogged spark arrestor or even bad spark plug can also result in the weed eater to cut out when revved or at any other time as well.
Even bad gas or moisture in the gasoline can also cause your weed eater to cut out when revved or even cause it to start and die or not start at all.
Also an incorrect oil to fuel mixture or even straight gasoline can cause the engine of the weed eater to stall when revved.