Chainsaw Repair

My little Poulon 3416 is not providing anywhere near enough chain oil and I am burning the bar. There's just a wisp of oil coming out where before it was at enough to keep the bar in shape. The saw is maybe five years old and doesn't usually cut more than a few hours a year... with one year where probably did fifteen hours.

I drained the bar oil, refilled with a thin oil, washed around, and drained again, hoping to clear anything in the reservoir. I cleaned under the bar and all around that area, blowing it dust/chip free and very clean. I found that little hole in the slot under the pressed sheet metal chain guide where I guess oil is supposed to come out and lube the chain and I cleaned that. I even blew some air into that hole... it gushed an ounce back out the hole when I stopped.  But, it still doesn't oil the chain properly when running.

How does this oiler work? Is there some sort of pump in there? Is it strictly gravity feed? What the relationship between the little hose that plugs in at the bottom under the chain area and the hole/slot where it looks like it's supposed to oil the chain?  And for testing: should it oil the chain when I just rotate it by hand or must the saw be running for it to deliver oil?

Thanks for any insight. I'm very mechanical, but I don't know much about chainsaws, as you might be able to tell! Let me know what to try.

There is a metal spring worm gear that turns on the crank that turns the nylon oil pump gear.  Many times trash gets behind this area and it stops it and strips out the nylon gear.

Also check this first. The strainer screen in the oil tank clean it and check and make sure oil tube is clear of fines and blockage to oiler.  Then to bar oil mount area.

All this is easy to do. Takes pics so you know how it all goes back.

Inside the oil tank. Spring type deal or a strainer on end of line in tank.

Bring piston past ports. Put some pull cord inside cylinder. Now try and take piston to the top and it should stop beforehand.
Take a punch and hammer and hit clutch support ( NOT SHOE ) clockwise off to the right.

Got it, thanks. 

The pump gear looks fine. Pump seems OK from what I can see, no visible wear?

So, it has to be the strainer?  Is there any way to get to that from outside, short of splitting the whole case?