The Dodge Cummins, like all diesel engines, needs to be heated before the engine will start correctly. If your engine is not starting when cold but starting when warm, chances are there is a problem with the heater. Follow a few steps to diagnose where the problem is and how you can fix it.
Turn the ignition on and look for an orange light that looks like a picture of a coil. This is the indicator that the engine is being heated. Do not start the engine until this light goes out.
Open the hood and locate the grid heater that heats the engine before startup. If the engine starts without smoke or stumbling in warm weather, then this is probably the problem.
Use the voltmeter to check the wires feeding the heater for power. If there is no power, trace the wires back and see whether they are broken or grounding out on something.
Examine the terminals on the grid heater to make sure it has not burned through the terminals and there is no buildup of dirt. Clean the terminals if needed to make sure the connection is working.
Check the gap between the terminals to make sure they're not shorting out on one another. If they are, clean and change the terminals to prevent them from shorting.
Replace the grid heater if your Cummins still will not start. That will allow the engine to heat properly.
