Replace the failed Glow Plugs in your 2008-2010 Ford 6.4L Powerstroke. Commons symptoms of a bad glow plug can include a check engine light, hard starting, misfire/rough idling, loss of power, white or black smoke, or a decrease in fuel economy. If one or more glow plugs fail, the combustion chamber won't have the necessary heat required to ignite the fuel. It may take several attempts at starting the vehicle before achieving ignition, depending on the outside temperature. In freezing winter temperatures, it is also possible for a diesel to not start without operational glow plugs. 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. 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.