I am looking for a way to kill fuel supply to the engine as an anti theft device. My truck (2004 Dodge 2500 5.9L Cummins) has the factory alarm, but I am not sure exactly what this alarm does as far as interrupting fuel supply, starter kill etc.

I don't think the anti-theft is the problem.
On GM vehicles, the anti-theft system will not allow the engine to crank, or get fuel or spark. If it cranks, you have a different problem.

Corrosion at the battery cables first. After that, remove the alarm system. Fix the wires as you go.

Hi, im a retired ford tech, with alot of experience on ford anti theft . Now if you are asking about a built in oem factory anti theft, your not going to be able to bypass it. Now to answer your question, I would say your factory anti theft IS NOT causing your issue. It will make it unable to start,it doesnt kill anything else.

Unfortunately if you are referring to the factory anti-theft system - it will have to have computers replaced. Once the Engine Computer sees a Theft Alarm request it will remain there forever and it will shut down the fuel system until seeing an OK To Start from the Theft Alarm.
If it is after market alarm - find it and disconnect wiring - restore connections to original
does that help?
If you are having trouble with the system? Make sure the battery is good and fully charged. There are entry switches on the back side of the lock cylinders on both front doors (probably knocked off when the door is "Slim Jim'd") and the trunk lock.
If your battery is dead and you try to jump it - you will have to turn off the alarm again after hooking up the jumper

Hi Alejandro,

A kill switch is a simple switch that interrupts power to the ignition system. You can attempt to start by cranking the engine over, but power is prevented from getting to the ignition coil / spark plugs so the engine will never start.

A kill switch can be a stand alone anti-theft device or is often part of an anti-theft system - that is operated by the driver often from inside the car. They can be as simple as a small toggle switch that is hidden away or can be related to requiring that the driver's foot be on the brake and the left directional must be on (or other combination of a number of devices) in order to start.

The simplicity of the kill switch relies on either (1) the stealthiness of its location or (2) method of disabling the switch to allow the engine to start and run (as described above). Since most are operated from the driver's seat, feel / look around under the dashboard, seat, console, etc. for a switch or other non-factory or suspect device that can be manually operated. Operate the device and attempt to start the vehicle.

Good luck!

Check the help links mentioned below :---Relearn Theft deterrent module? http://technoanswers.blogspot.com/2012/01/relearn-theft-deterrent-module.html
---------theft deterrent module Relearning? http://howtobyme.blogspot.com/2012/01/buick-theft-deterrent-module-relearning.html
--------Engine will not crank after relearning Theft deterrent module? http://howtobyme.blogspot.com/2012/01/engine-will-not-crank-after-relearning.html
--------Can car radio code block Passkey anti theft system ?

http://schematicsdiagram.blogspot.com/2011/12/can-car-radio-code-block-passkey-anti.html
Car Factory Alarm will go off? http://repairhelpcenter.blogspot.com/2012/01/toyota-avalon-factory-alarm-will-go-off.html
---------Car will not start security lock out? http://technoanswers.blogspot.com/2011/12/car-will-not-start-security-lock-out.html
---------Alarm will not disengage? http://technoanswers.blogspot.com/2012/01/ford-pickup-alarm-will-not-disengage.html
--------This will help.For more info keep updated.Thanks.

First, check all the fuses in the interior fuse panel. I believe that one is located just under the left knee area of the dashboard or behind a hidden panel that you access on the side of the dash when the drivers door is open. Second check all the fuses and relays in the power distribution box under the hood, drivers side near the air cleaner box. If all fuses are good, I make it a point of checking the timing belt. The easiest way to do that is do a compression check. If the timing chain is broken you will not have any compression on several cylinders. If you have a fuel injected motor and you should, at the end of the fuel rail(s) there is a black cap and when you remove that you can put a pressure gauge on it and check your fuel pressure. Make sure the ignition is in the on position when you check it. Finally, if everything else checks out replace the coil pack which has the ignition coil built into it. Now all of this assumes you do not have an alarm with a starter kill switch or anti theft device installed. If you have an alarm installed on the vehicle that is not factory equipment, disconnect the main power wire for the alarm and try starting.

Check if equipped for anti theft system. Usually the anti theft will allow for initial spark and then kill the fuel injectors!
Disconnect the battery and have it recharged and tested, if it fails the test replace it. Use the key and manually lock and unlock the drivers door if the alarm is still set, There is a switch attached to the door lock that disables the anti theft. If the driver's side is defective switch you have to do this from the passenger door.

Hope this helps?

You cannot since the anti theft system is integral to the ignition and fuel delivery systems.

Sorry.

when they installed the alarm they also in stalled a valette switch on your ride this is to shut off the alarm im looking for the site for your remote that has the way to get your code back in but for now find the valette switch which can be under dash or right side driver kick panel you might have to hold the vallette switch for 5 seconds till it goes off i will post the other solution once i find it for you