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Methods and systems for cutting off the supply of fuel to an engine in response to engine turn-off. A fuel cutoff solenoid or functionally equivalent device is connected to a source of electrical power in response to detection of conditions representing engine turn-off. One method for cutting off th

Methods and systems for cutting off the supply of fuel to an engine in response to engine turn-off. A fuel cutoff solenoid or functionally equivalent device is connected to a source of electrical power in response to detection of conditions representing engine turn-off. One method for cutting off the supply of fuel to the engine comprises the following steps: detecting whether ignition pulses are present; and then activating a device for cutting off the supply of fuel to the engine in response to detecting the cessation of ignition pulses. The fuel cutoff device is activated by connecting it to either a battery or an output of a generator being driven by the engine. In the latter case, the rotor is grounded and a bipolar transistor is bypassed in response to detection of conditions representing engine turn-off.

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1. A method for cutting off the supply of fuel to an engine, comprising the following steps:detecting whether ignition pulses are present; andactivating a device for cutting off the supply of fuel to the engine in response to detection of a change from a first state in which ignition pulses are pres

1. A method for cutting off the supply of fuel to an engine, comprising the following steps:detecting whether ignition pulses are present; andactivating a device for cutting off the supply of fuel to the engine in response to detection of a change from a first state in which ignition pulses are present to a second state in which ignition pulses are absent. 2. The method as recited in claim 1, further comprising the step of deactivating said device at a predetermined time subsequent to said activating step. 3. The method as recited in claim 1, wherein said activating step comprises the step of energizing a solenoid. 4. The method as recited in claim 3, wherein said step of energizing the solenoid comprises electrically connecting the solenoid to a battery power supply. 5. The method as recited in claim 3, wherein said step of energizing the solenoid comprises electrically connecting the solenoid to an output of a winding in a generator driven by the engine. 6. The method as recited in claim 5, further comprising the step of connecting a rotor winding of the generator to ground in response to detection that ignition pulses are not present, said winding connected to said solenoid being electromagnetically coupled to said rotor winding. 7. A system for cutting off the supply of fuel to an engine, comprising:a battery power supply;a first device that cuts off the supply of fuel to the engine when energized by said battery power supply and does not cut off the supply of fuel to the engine when not energized by said battery power supply;a second device for connecting said first device to said battery power supply in a first state and disconnecting said first device from said battery power supply in a second state; anda control circuit that causes a change of state of said second device from said second state to said first state in response to a change from ignition pulses being present to ignition pulses being absent. 8. The system as recited in claim 7, wherein said first device comprises a solenoid. 9. The system as recited in claim 7, wherein said second device comprises a relay. 10. The system as recited in claim 7, wherein said control circuit has an input for receiving signals representing ignition pulses being sent to said engine. 11. A method for cutting off the supply of fuel to an engine being used to drive an electric generator, comprising the following steps:detecting whether ignition pulses are present; andcoupling a rotor winding of the generator to ground and a stator winding or coil of the generator to a fuel cutoff device in response to detection of cessation of ignition pulses. 12. The method as recited in claim 11, wherein said step of coupling the rotor winding to ground has the effect of shorting a power switch. 13. The method as recited in claim 11, further comprising the steps of opening said connections at a predetermined time subsequent to said coupling step. 14. The method as recited in claim 11, further comprising the step of rectifying said generator output, wherein said fuel cutoff device comprises a solenoid that is energized by the rectified generator output. 15. A power generation system comprising: an engine, an engine ignition controller for providing ignition pulses to said engine, a stator winding or coil for providing a generator output, a rotor winding driven to rotate by said engine, and a fuel shutdown system for cutting off the supply of fuel to said engine, wherein said fuel shutdown system comprises:a first device that cuts off the supply of fuel to the engine when energized by said battery power supply and does not cut off the supply of fuel to the engine when not energized by said battery power supply;a second device having first and second states, said rotor winding being connected to ground when said second device is in its first state and not connected to ground when said second device is in its second state;a third device having first and second states, said stator winding or coil bei ng coupled to said first device when said third device is in its first state and not coupled to said first device when said third device is in its second state; anda control circuit that causes a first change of state of said second device from its second state to its first state and a second change of state of said third device from its second state to its first state in response to cessation of ignition pulses. 16. The system as recited in claim 15, wherein said first device comprises a solenoid. 17. The system as recited in claim 15, wherein said second device comprises a first relay and said third device comprises a second relay. 18. The system as recited in claim 15, wherein said control circuit has an input for receiving signals representing ignition pulses being sent to said engine. 19. The system as recited in claim 15, further comprising a field current controller for supplying current to said rotor winding, said field current controller comprising a power switch that is shorted when said rotor winding is connected to ground. 20. The system as recited in claim 15, further comprising a rectifier for rectifying the output of said stator winding or coil. 21. A method for cutting off the supply of fuel to an engine being used to drive an electric generator, comprising the following steps:detecting whether the engine has been turned off; andconnecting an input of a fuel cutoff device to an output of a stator winding or coil of the generator in response to detection of engine turn-off, said fuel cutoff device being energized by said generator output. 22. The method as recited in claim 21, further comprising the step of connecting a rotor winding of the generator to ground in response to detection of engine turn-off. 23. The method as recited in claim 21, wherein a bipolar transistor is bypassed by grounding of the rotor winding. 24. The method as recited in claim 21, wherein said detecting step comprises the step of detecting whether ignition pulses are present.