ok i have a 99 7.3 i know the glow plugs are bad because it wont start in cold weather unless i plug it in then it starts fine so i went to the parts store paid $96.00 came home to put them in i thought that they were like spark plugs and screwed in to the heads by the exhaust manifold but no that would be to easy can some one tell me where they are and im hoping your not going to say under the valve covers

 

ok never mind it turned out that it was not the glow plugs any way so im glad i didn't put them in it was the glow plug selanoid on top of the motor if any one ever has this problem the selanoid should have power on oneside all the time and when you turn the key on the switch wire will bridge the power to the other pole on the selanoid and that sends power to the glow plugs so if you have truble starting your 7.3 look on top of the motor for a selanoid and see if you have power on both legs of it when you turn the key if not thats most likely your problem if i was able to help one person all this was worth it have a good day and god bless DOUGSTRUCK

 

Thanks for the update and sharing some valuable information for our readers who may need it up the road.

 

That's actually a fairly common problem. I've replaced that solonoid in my '96 several times. Easy to diagnose and easy to replace.