Hey guys I have a 2007 2500 5.9. My truck will actually start by turning the key, but if I touch the battery cables to the terminals it will start cycling the crank without starting. I took the starter off and had it tested and the starter is fine. I can disconnect the sylanoid and it will still cycle the crank. I disconnected the ignition switch and it will still try to cycle the crank. Last thing I can guess is the starter relay but I can't find it.

 

There is no relay it's a direct wire! Not sure what your saying? Motor cranks by itself? Either a bad starter or the wire is rubbed thru and touching power somewhere. Which would be weird! You disconnected the other possible causes! There is a yellow wire on the drivers side firewall disconnect that let me know what it does then. Ign should NOT work with it disconnected!