Oil pump 266 xp

SOURCE: oil does not lube chain on my chain saw, huqvarna, any ideas

It appears from the IPL and OM this saw does not have an adjustable oiler.
OM example here (2005 - may not be your saw):
http://weborder.husqvarna.com/order_static/doc/HOUS/HOUS2005/HOUS2005_O0501001.pdf
IPL example here (2005 - may not be your saw):
http://weborder.husqvarna.com/order_static/doc/usa/2005/I05000/I0501901.pdf

I know you have done this, please verify whether or not you get the ooze with the saw running.
Oil System Plugged:

1. Remove the clutch cover, bar, and chain, clean the bar groove, any holes and passages on the rear of the bar (both sides, consider rotating the bar), if equipped with a sprocket nose ensure it rotates easily at least one complete revolution. Clean the saw oiler hole and channel. Insert a blunted, hooked piece of wire through the oil filler hole and pull the hose in the oil tank out. Pay attention to the screen or filter on the free end (clean or replace, difficult to determine serviceability). Start the saw and see if it oils when revved up (oozes down side of saw). If yes reassemble your saw. If no, continue with 2.
2. Work your way through the linkage (use IPL to identify components and locations) cleaning and replacing any defective parts as you go. Carefully check the hoses for cracks especially at bends and connections. If equipped with an oil pump it is usually behind the clutch (clutch is a left handed thread). Please make extensive notes & some digital pictures will help during reassembly.

SOURCE: in what order is a

The tensioner is in the crankcase, insert the screw through the hole in the crankcase, thread the square plastic block onto the screw followed by the metal adjuster pawl, the plastic block shold come all the way up the thread and lock into the recess in the screw.