2-cycle engine question

Background: Homelite chainsaw runs, but it's not oiling the chain. The oiler seems to require pressure from the engine, which (1) pressurizes the oil reservoir and (2) operates a diaphram pump.

The pressure for these actions seems to come from a port drilled into the crankcase. From my vague knowledge of 2-cycles, I think there would sometimes be pressure there (during the exhaust stroke?) - that's why it needs reed valves?

My question is, if there is crankcase pressure, would that be affected by whether the spark plug was installed or not? When I spin the engine with a drill (plug removed), I do get some action on the pump diaphram, but not very much. I'm wondering if this is part of the problem, or just a symptom of cranking with the plug out.

Thanks, George

I may show my ignorance, but as I remember it, there is pressure on the crankcase when the piston is going down (the power stroke). The exhaust gas exits via a port in the side of the cylinder, usually.

The downward travel of the piston creates pressure in the crankcase against the reed valves which forces the mixture into the cylinder.

As the piston goes back up, vacuum is created and a fresh charge is drawn into the crankcase through the reed valves.

So there is alternating vacuum and pressure in the crankcase.

If your piston rings are good, the crankshaft seals are not leaking, and the reed valves are working as they should, I don't think the spark plug being out is going to decrease the pressure in the crankcase enormously.