The glow plugs in a Ford diesel engine will need to be replaced every 30,000 to 40,000 miles. The glow plugs heat the diesel fuel so that the engine compression is sufficient to cause an explosion (which in turn produces power in the engine cylinders). Over time, glow plug electrodes wear down. When this happens, you'll need to replace the glow plugs.
Pull the glow plug wires out of the top of the engine. Only work on one glow plug/wire at a time. You may need to wiggle the end of the plug back and forth as you are pulling up on it to remove it. Lay the end of the plug on the top of the engine.
Connect the socket extension to the glow plug socket and then connect this assembly to the socket wrench. Lower the socket down into the plug well and orient the wrench so that you are "grabbing" onto the end of the glow plug.
Turn the plug counterclockwise to remove it.
Pull out the plug with the socket.
Remove the old plug and put the new glow plug into the socket with the electrodes facing out (down into the engine).
Insert the new plug into the engine and turn clockwise to tighten.
Secure the plug wire back down into the plug well and over the top of the glow plug.
