Chainsaw Oiler Doesn't Work

I recently purchased a ~25 year old Craftsman chain saw, model number 358.355051. I believe this saw was made by Poulan. The chain oiler does not work and it leaks oil. The leaks are due to two gaskets that are missing. I made gaskets using sheet gasket material and an Xacto knife. Following the exploded view diagram on Sears’ parts website I removed the oil pump. I am baffled as to how it’s supposed to work. It’s a small, round black plastic thing with an aluminum disk on one end that might be an oil metering device. On the other end is a small plastic barb, maybe 1/8 inch in diameter, that has nothing connected to it. It certainly looks like something should be connected there. The pump assembly mounts low on the crankcase in the front corner near where the chain enters the saw. I see no mechanical connection or attachment to power the pump. The hole in the saw casing (cast metal—no plastic!!) where the oil should come out is not clogged. On the inside of the casing there is no hose or tubing attached to this oil port. The parts diagram also shows an oil filter which is missing on my saw.

Can someone explain how this oiler is supposed to work and what might be wrong with mine? Should there be a hose that runs from the barb to the oil hole in the casing?

 

The oiler works off of crankcase pressure, so there is no mechanical connection to it. There is a check valve screwed in behind the clutch on the side which might need replacing, and there is a rubber check valve that the crankcase pressure enters through that also might be bad.