How to clean the carbon on the injector nozzle seat.
Rotate engine to bring piston up to TDC on the injector your working on. See below how.
Remove injector and glow plug.
Spray injector bore with carburator cleaner, PB blaster, Kroil or a like substance. WD40 doesn't work to good.
Remove copper washer from the seat. Large screw driver, driven into washer hole will usually do it. If it didn't come out with the injector.
With a seat reamer, use light pressure only enough to cut carbon, it's possible to "ripple" the seat.
If seat is grooved, then enough pressure to carefully cut seat.
With a 10 ga. shot gun bore brush, (RLDSL) in a variable speed drill.
Keep spraying with cleaner to soften carbon.
With a vacuum cleaner hose over the injector bore, spritz compressed air in the glow plug hole, this will remove any debris from the precup, but not any liquid, but that should evaporate.
The engine rotates in a clockwise direction as seen from the front of the truck, and for every 1/4 turn of the engine(crank) each next piston will arrive at TDC. So, When the line on the vibration damper is at the 2 oclock position, cylinders 2 and 5 will be at TDC. When the mark is at the 5 oclock position, cylinders 7 and 6 will be at TDC, 8 oclock has cylinders 3 and 8 at TDC, and back to 11oclock, 1 and 4 will be at TDC.
Cylinder numbers are assigned 1,3,5,7 on the left passenger bank from front of truck to back, and 2,4,6,8 on the driver's side, front to back. Firing order is 1,2,7,3,4,5,6,8.