1999 F250 7.3 Motor Starting Trouble

[cweich]

I have a 1999 F250 with a 7.3 w/manul 5 speed. I Parked the truck for and 1 hour and it would not start, I assumed it was the CPS, but the truck still did not start, i heard a clicking or buzzing noise under the hood, it was coming from the fuse/relay panel next to the fender on the drivers side, one of the relays buzzed while the wait to start light was on. i think its the third one up, its for the injectors, i swaped it with the blower motor relay just to try it, and the truck took right off, this was a week ago, i replaced the relay, now it is starting to buzz again, what will cuz this to happen? Thanks for your help!