the automatic vehicle anti - theft system which comprises the present invention is described herein with respect to one embodiment . that embodiment is an attachment to an automotive vehicle having a conventional wiring harness for a battery 50 including a key operated ignition switch s 1 furnishing switched electrical current to the ignition , radio , vent , etc . the present invention includes an electrical module 51 connected by electrical cable 71 to the positive terminal 64 of the battery 50 and by electrical cable 72 to the negative terminal 65 of the battery 50 . the positive terminal 64 of the battery 50 is also connected to key operated ignition switch s 1 supplying switched electrical current to the electrically controlled fuel supply system 53 , the momentary switch s 2 and the mode switch box 52 . the momentary switch s 2 is connected by electrical cable 73 to ignition switch s 1 and by electrical cable 74 to electrical module 51 . the momentary switch s 2 should be either hidden , such as underneath the dash , or undetectable . it may be any convenient switch , including a magnetic switch , operated by a hand held magnet , a foil or tape switch , operated by finger pressure , or an aperture switch , operated by inserting a pencil point or sharp object into the aperture switch . the electrically controlled fuel supply system 53 is connected by electrical cable 75 to ignition switch s 1 and by electrical cable 76 to electrical module 51 . the electrically controlled fuel supply system 53 may be a solenoid controlled fuel valve inserted into the fuel line , may be the motor of an electric fuel pump or may be relay for another fuel control device . in any case , only when electrical current flows through the device , does fuel flow to the engine . within the electrical module 51 is a scr transistor t3 which is an electronic valve which controls flow of electric current from electrically controlled fuel supply system 53 , through electrical cable 72 , to the negative terminal 65 of the battery 50 . the momentary switch s 2 is connected to the gate of scr transistor t3 , through resistors r6 , r5 , and r1 , within electrical module 51 . also within the electrical module 51 is a npn transistor t1 whose emitter is connected to scr transistor t3 and whose collector is connected , through electrical cable 72 , to the negative terminal 65 of battery 50 . the base of npn transistor t1 is connected through bias resistor r4 to the emitter , through resistor r7 and resistor r11 , to electrical cable 77 and the switched electrical current . the base of npn transistor t1 is also connected , through resistor r7 , to the open door switch s 3 . the valet parking override switch s 5 , resistor r9 , and resistor r10 , of the mode switch box 52 are all connected by electrical cable 80 through electrical module 51 , and electrical cable 71 to the positive terminal 64 of the battery 50 . the electrically controlled fuel supply system 53 and the light emitting diode l2 are connected to the scr transistor t3 of the electrical module 51 through electrical cable 79 . within the mode switch box 52 is a first light emitting diode l1 connected through resistor r9 to electrical cable 78 through the electrical module 51 and electrical cable 71 to positive terminal 64 of battery 50 . the light emitting diode l1 is also connected through electrical cable 78 to electrical module 51 to the anode of scr transistor t2 , and is a red pilot light . also within the mode switch box 52 is light emitting diode l2 connected through resistor r8 to electrical cable 77 and the switched electrical current of ignition switch s 1 . the light emitting diode l2 is also connected to the anode of scr transistor t3 , and is a green pilot light . referring to fig2 the values of the components may be the following : the present invention operates in any one of three modes . the first two modes are protection modes and the third mode is an unprotected mode . the first , or normal , mode is a combination anti - theft mode and anti - hijack mode . the open door override switch s4 is closed , enabling the open door switch s 3 . the valet parking override switch s5 is open , disabling the valet mode . the owner closes the ignition switch s 1 and presses the momentary switch s 2 . this applies a current to the gate of scr transistor t3 , opening the current through the solenoid controlled fuel valve . after the scr transistor t3 is turned on , it remains on , until the ignition switch s 1 is opened by turning off the key . if a thief turns on the ignition switch s 1 , but fails to press the momentary switch s 2 , the motor will start . however , the electrically controlled fuel supply system 53 remains closed and the motor will stop in several seconds for lack of fuel . the switched electrical current will be supplied to the electrically controlled fuel supply system 53 , but the scr transistor t3 will not pass the current . thus the thief who has a key will be able to start the vehicle and run a short distance . the motor will then stop . the ignition and starter will work , but the vehicle will give the appearance of an engine malfunction and the thief will have to abandon it to avoid apprehension . in the first , or normal mode , the owner and vehicle are also protected against hijacking by the anti - hijack mode . this mode operates automatically by anyone opening a door during operation . if a hijacker forces the owner to open the door , the owner may leave the vehicle . the hijacker may get into the vehicle and drive away . however , in several seconds the motor will stop and the hijacker will not be able to restart the motor . in the anti - hijack mode , when a door opens , the open door switch s 3 is closed . this lowers the voltage on the gate of npn transistor t1 . this in turn blocks current to flow through npn transistor t1 which raises the voltage on the cathode of scp transistor t3 which causes scr transistor t3 to close . this turns off the electrically controlled fuel supply system 53 , causing the motor to stop . the motor can be restarted only by closing the door , thus opening the open door switch s 3 , and then by closing momentary switch s 2 . neither the location , nor the function of momentary switch s 2 will be apparent to a hijacker . it will often be convenient to disable the anti - hijack mode to allow the owner to pick up or let off passengers . the vehicle may be operated in the second of the two protection modes by opening the open door override switch s4 . this disables the open door switch s 3 and leaves the npn transistor t1 open , so that npn transistor t1 cannot turn off scr transistor t3 and close the electrically controlled fuel supply system 53 . the third mode is the valet mode or unprotected mode . the owner turns valet parking override switch s5 on . this supplies current continuously to the gate of scr transistor t3 , effectively grounding the electrically controlled fuel supply system 53 . the electrically controlled fuel supply system 53 thus operates whenever the ignition switch s 1 is closed , and there is no evidence that the vehicle is protected by an automatic vehicle anti - theft system . the light emitting diode l2 , which may be a green pilot light , is on whenever the electrically controlled fuel supply system 53 is open , supplying fuel to the engine . the light emitting diode l1 , which may be a red pilot light , is on whenever the valet parking override switch s 5 is closed and the automatic vehicle anti - theft system is in the valet mode or unprotected mode . as shown in fig3 a second version of the circuitry allows the invention to operate with a fuel supply system 53 normally on , so that a failure within the protection system will not cause the vehicle to stop . cable 76 from electrical module 51 leads to inverter 85 , in order to change the polarity of cable 86 from negative to positive . the protection modes therefore have the polarity not positive for cable 86 . the cable 86 leads to alarm module 87 . a presence sensor 88 and open door switch s3 also lead to the alarm module 87 . the alarm module 87 is a modification of known vehicle alarm systems such as disclosed in automatic vehicle burglar alarm , popular electronics , april 1970 , pages 59 et . seq . the alarm module 87 is connected to the relay 89 which controls the siren 90 , normally open fuel valve 91 , and starter 92 . a trigger signal from open door switch s3 or presence sensor 88 will turn alarm module 87 on . a positive signal from inverter 85 will turn alarm module 87 off . the alarm module 87 has a time delay to allow the operator to leave the vehicle ( 1 min .) and to reenter the vehicle ( 6 sec .) before the protection mode is turned on . when alarm module 87 activates the protection mode , relay 89 is activated and siren 90 is turned on , normally open fuel valve 91 is closed , and starter 92 is disabled . as shown in fig4 third version of the circuitry allows the invention to protect fuel injection or turbo engines by turning them off after a time delay , since as soon as the high pressure electric fuel pump is disabled the engine will stop . in this version electrical module 51 is connected to a delay module 93 , which allows the engine to operate for a period ( 1 min .) after open door switch s3 is closed before relay 94 is activated . when it is activated , it blocks starter 92 , fuel injection pump 95 and an optional ignition block 96 . it will thus be seen that the objects set forth above , among those made apparent from the preceding description , are efficiently attained and , since certain changes may be made in carrying out the above method and in the article set forth without departing from the spirit and scope of the invention , it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense . it is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described , and all statements of the scope of the invention which , as a matter of language , might be said to fall therebetween .