We have a similar Jabsco pump-on-a-bucket device.
At the risk of telling you what you already know, the oil has to be hot before the pump can successfully pull it through that narrow stick-it-down-the-dipstick-tube plastic tube.
I once had to drain all 12 quarts of oil out of one of our Lehmans due to a "mishap," and I could not run the engine to warm up the oil. It took over an hour for the Jabsco pump/bucket thing to pull a gallon out. So we gave up and removed the sump drain plug instead.
Normally, we start up the Lehman that's going to get the oil change and run it under load (in forward at high idle) until the oil filter is warm to hot-ish to the touch. From a cold startup, this usually takes about 15 minutes or so. We then shut down, punch a big hole in the top of the oil filter, and then procede to use the pump/bucket thing to pull the oil out of the dipstick tube. When the oil is warm/hot like this, it takes about ten minutes to pull all three gallons out.
While your Volvo is a different animal than our Lehmans, the principle is the same, I think, although I doubt punching a big hole in the oil filter will gain you anything other than a mess, I think.
If you ARE warming up the oil before attempting to suck it out with the pump/bucket thing, then I don't have any suggestions for you as I have zero famiarity with your engine.
Bruce's point about making sure the plastic tube is at the bottom of the sump but not pushed down any farther is spot on. On our engines, the dipstick tube aims the plastic suck-out tube right down the side of the sump pan. So I can feel when the end of the tube comes in contact with the bottom of the pan, at which point I pull the tube up a quarter of an inch or so. If I were to keep pushing, the tube would curl up and the end may well come out of the oil.