Offline Problems

how can i make it so players loose permission when they go offline as people are able to keep control permantly 

My recommendation to limit the usage of the excavator is to set

"Enable engine loot after it is started to add diesel": false,​
To prevent adding fuel continously

Also to limit the stack size of the fuel for the axcavator
plugin like stack-item-storage or ChestStackMultiplie can do that

- Setting a cooldown between usage for players. (30 minutes in this example). but if you set it to 1440 minutes. Players will be limited to using it once per day.
"CoolDown before a player or team can restart the excavator (0 is disabled)": 30.0,​