I installed an Air dog on my 2000 CTD in May 2005 and it has worked well ever since. Do you have a fuel pressure guage? If so, what psi reading do you get when you first turn the switch on prior to cranking the engine? The Dog is supposed to be set at about 16 psi. It should register that amount prior to cranking the engine, then fall off to zero by the time you actually try to start the engine. Check to be sure your fuel lines are all tight at their connections. If air gets into the line between the Dog and the injection pump you have lost half of the reason for installing it. Once your engine starts and runs smoothly, you should be able to maintain 16 psi plus or minus at all times, even on the long hills pulling a load.