An electrical grounding system for grounding the ignition system of an internal combustion engine on a tractor or the like to prevent the starting of the engine and to stop the engine when operating unless switches of the grounding system are so set by operating conditions and positions of parts of the tractor or the like. The grounding system is arranged so that unless switches in an electrical circuit of the grounding system are set or maintained in proper position by operations of the tractor or the like, (such as the clutch of a grass cutting unit carried by the tractor or the like, such as the clutch of the drive mechanism of the tractor or the like, such as by the occupancy or non-occupancy of the seat of the tractor or the like, or such as the connection or dis-connection of a grass catcher to the tractor or the like) the ignition system of the engine is grounded or short circuited and the engine is inoperative.
