Oh Lemme guess...the Throttle was reading 0%?
This does not necessarily mean the engine is off, infact it might be that the engine is at "Theoretical idle power".
The function that does all the engine calculations/ fuel consumption is only set to update if "engineOn == true". So once the engine is turned off either by the user, fuel exhaustion or some other condition, thrust is no longer generated and other conditions including fuel consumption stops.