It appears something got messed up with the most recent update. When using excavator, you have to put fuel in, "turn on" the engine, but you have to go select what you want to mine before it starts moving. However, when you try to select something, it won't let you and it says "Giant excavator is currently in use by ."

My guess is they changed how and where the OnDieselEngineToggle(d) is called.

Yep PLS Update PLS 

Hi, Revision 0.4.9 was an update for the OnDieselEngineToggle hook change. On my system, the plugin works fine
from what you describe, you seem to be using an older version of the plugin.

Apologies. I guess that was the issue. Apparently I wasn't watching the plugin, so when it was updated I never noticed. My mistake. Newest version works fine.