Truck Repair: glow plugs, glowplugs, glow plugs

Question
my truck does not start on cold mornings.  I just replaced the glow plugs and that did not help.  could it be the relay?  and where exactly is that located? 1997 ford f250 turbo diesel

Answer
The Glow plug relay is located on top the engine near the fuel filter housing.  There is one post that is a constant hot (Large post , make sure it has power)  and have someone turn the key to Run position.  Test the small post and make sure it gets signal power, when it does, the other large post should get power as well.  If you get constant power, and signal power, but no outgoing power on the relay , it is bad.
 In the future; you can test all your glowplugs by hooking a test light to the + side of the battery.  Then touch the test lead to the tip of the glow plug(wire unhooked, still installed in the engine) If the light lights up on each of them, they are good.  The new P.S. engines RARELY have glow plugs go bad.
Let me know if you need further help