7.3 Missfire?

[Ronny'02-7.3]

Hey guys. A buddy of mine is having a little problem, maybe someone has experience. He has a 2001 7.3 CC 4x4. The truck runs rough and he says the only codes are #1 & 5 cylinders not firing. I just talked to him a little about it today, so I don't have a lot of details. He says it is pretty constant. i also wonder how the cylinders are numbered.any ideas would be appreciated.
Ronny

[99Smokin73Stroker]

Ronny it is probably an injector problem but i'm not positive!
As for the cylinder numbers they are as follows - The numbers go front to rear
Right passenger side.....1-3-5-7
Left drivers side...........2-4-6-8
If you need to know the firing order is 1-2-7-3-4-5-6-8