alright i pulled the head and found #2 piston melted and a broken ring. do i still need to pull the motor if the cylinder walls are still good or can i just do an inframe and replace the piston and rings.

 

You need to find why it melted! I would suspect the oil cooling nozzle is plugged.
Do you know if it ever had a fram oil filter on it? They are known to seperate and plug the nozzles.

 

i honestly have no idea i just bought it for a steal a couple of days ago and they thought it had a hole in the piston and didnt want to put the money into it to get it fixed but its cheaper to fix this one than to buy a good running diesel 4x4 where i live at.

 

and could that plugged nozzle cause the oil pressure to drop after it runs for about a minute

 

Sorry I do not know what you will need to do the fix the engine but if you are refering to the in dash oil pressure gauge, you need to know that it is not a true oil pressure gauge. It is an indicator controled by the computer. You have a 0 or 6psi switch that the computer sees and as long as there is at least 6psi it will indicate what the computer thinks the oil pressure will be based on the temp of the engine and RPM. Also it takes around 4 seconds for the oil pressure to come up on a cold start. The computer allows for this and will show pressure up to 30 seconds after a start even if there is no pressure. This could be the cause in the drop in pressure that you are seeing and you probably do not have pressure at all.

You will need to put a real gauge on it to know what is really happening with you oil pressure.

 

It is going to be doubtful that you can do an inframe. Chances are the cylinder is scored from the broken ring and will require a bore job. At the least, there will be aluminum from the melted piston on the cyl walls and that will need to be honed.

It will need to be looked at by a machine shop to know for sure (we can't see your engine on the forum).

Melted piston is usually caused from running the engine with too high an egt. Other pistons may be affected too. It could have been a leaky injector that caused this as well. It is difficult to do internet forum diagnosis.

A plugged piston oil squirter won't cause a drop in oil pressure. The way that piston squirter is placed (along an oil gallery) means it would just be bypassed. the 2005 uses big "J hook" style of piston squirter... fairly large diameter there; hard to imagine that would clog but anything is possible.