Replace the faulty Glow Plugs and restore proper operation in your 2003-2007 Ford 6.0L Powerstroke. A glow plug is a heating element that is used to heat incoming fuel and air. This is designed to help aid the combustion of fuel in a diesel engine especially during startup. This heat can be necessary for a diesel engine to start, run, and function optimally especially in cold weather conditions. Many diesel engines utilize one glow plug in each cylinder, either in the pre-chamber or in the combustion chamber. When a glow plug fails to work properly, the combustion chamber doesn't have the necessary heat that can be required to help ignite the fuel. Depending on the outside temperature, it may take several attempts at starting the vehicle before achieving ignition. In freezing winter temperatures, it is possible for a diesel engine to not start at all without operational glow plugs. Symptoms of a faulty glow plug include a check engine light (CEL), hard starting, rough idle/misfire, loss of power, black or white smoke, and a decrease in fuel efficiency. Shop glow plugs, harnesses, and controller/control modules from all the leading manufacturers such as Diesel RX, Dorman, Bostech, Ford/Motorcraft, Dtech, Alliant Power, GM/AC Delco, and Diamond Advantage By Navistar.