1993 7.3 IDI won't start
 

I have a friend trying to figure his pickup out and told him how great you guys are at helping. 1993 7.3 idi cranks with no fire unless plugged in. He's replaced the glow plug relay and another relay that looks the same on the fender. WTS comes on for about 6 seconds and can hear the relay clicking but when we crank it over it won't fire up. No code scanner available so unknown if there is any codes present no sevice engine light on though. Any help would be much appreciated.

I know stupid question but did you take a test light to see if you have power going to each wire from the relay to the plugs?

That's not a stupid question 1stgenman. After I posted this I told my friend how to test the glow plugs. He did and had 2 burned out. Replaced them and it runs like a top. Thanks for suggesting though. Everything helps.