Why is my 2003 Dodge Diesel hard to start when it is cold outside?

any diesel is hard to start when cold. your diesel should have a block heater somewhere. find the plug in and when vehicle is parked,plug the cord into a 110 outlet.that should solve your problem. this is all explained in your owners handbook. To add to this answer: Most diesel engines work off a set timer (they don't know the difference between -20 and plus 20 degrees) of around 15sec. A very popular solution used in Canada is to have the timer bypassed to a switch. The best type of switch to use is called a MOMENTARY, it only activates the plugs with your finger on the switch. Not touching the switch the plugs will work normally, but when you hold the switch on it will continue to run as long as you want (I know Toyota Landcrusiers glow plugs can run for a minute with no problems to the plugs. A shop that installs automatic car starters would be the best place to have the custom switch installed due to their common contact with the various vehicle wiring (not a dealership).