This sounds rather naive, but the last diesel I had was a '88 F350 7L. I now have an "05 F250 6L which has at least two - three bad glow plugs, but I cannot find them. I found the injectors, but I have a hand full of new plugs and cannot install them.

 

They're under the valve covers.

 

Oh! Thanks so much, I don't believe I would have ever thought to look for them there!

 

Not on a 6.0L, they are on the outside of the valve covers between the exhaust manifold and valve covers.

 

Eh, I was close. lol

 

I was going to reply to say they were under the valve covers too, but he said he'd found the injectors so I was at a loss as to why he couldn't find them. If you didn't pull the valve covers you didn't find the injectors, they're under the valve covers.