Hi, Received a Poulan Pro PPB1838, in poor shape, would not fire at all. So far, new plug(s), new fuel lines/filter/purge valve, new carb/gasket, new air filter. 120 lb. compression, exhaust appears clean, no scoring on piston. Has spark, can jump an 1/8" gap with a blue spark. Purge valve fills with fuel after 5 to 6 pumps.
Getting fuel as with plug out I can see vapor blowing out plug hole? Have carb needles at 1 1/2 turns each. Pulled fly wheel to check keyway. Reset coil gap. Disconnected kill wire, no change. Has fresh fuel 50:1 mix. Can shoot carb cleaner in and it will not even pop over. After multiple start attempts plug does appear wet, even tried flipping the fuel lines on the carb to no avail. This one has me stumped.

Try putting a couple of teaspoons of 2 stroke oil down the spark plug hole. 
 
This will increase the compression.  120 sounds ok but is actually somewhat lowish for this engine.
 
Also try adjusting the carb adjusting screws some. 
 
You shouldn't be able to see fuel come out of the spark plug hole normally, so it's very possible the lower end is flooded.   Hold the throttle wide open, no choke, and try.  I believe your getting spark AT THE PLUG, when grounded to the head, correct?
 
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I did try fuel down the plug hole, nothing. Definitely got spark, plug grounded to head.
To me it's like it looses spark under compression.  

I think I may have found something. I had the plug out, connected to the coil wire and grounded at the head. I was spinning over the engine with a drill when I noticed I had to have the engine spinning pretty fast before a spark would arc. Thinking about it, there is no way I could pull the cord to make it spin that fast. So maybe there is something going on with the coil? And that's why it's acting like it has no spark under compression.  I have 2 other saws, and it doesn't take a wicked pull on the cord to start either of them.
 

Stihl engines are notorious for having a very weak spark. 
 
Clean ground connections where the coil contacts the block, leave the "kill wire" disconnected.
Check for spark in a very dark area, pulling by hand.
 
It just takes a little of spark to fire off.  Spark plug could have a break inside the insulation, check for any looseness where the cap snaps on to the plug-it DOES happen.
 
I guess your not going to try some oil down the spark plug hole, can't help much if you won't try what's suggested..
 
Good luck.
 
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Sorry I did try the oil trick previously, didn't change it. I also cleaned the mounts and ground wire for the coil. I noticed the back of the coil was oil soaked, maybe messed up the coil? And yeah, I'm not seeing any spark at what I would think the flywheel speed would be under compression hand cranking. Had to spin the flywheel really fast to get a spark from the plug and my tester. I guess I'm in this far I might as well replace the coil and see what happens..

New coil arrived, installed, and she fired up on the third pull!

Excellent!!