I realize this this post is fairly old but I had a revelation the other day with my hand pump that really helps with the softness on the downstroke. Figured I would share for others with the same problem.
As mentioned above, first and foremost, the fluid level must be topped off or else air will get sucked into the pump and the top won't be going anywhere. I had a bad O-ring on my pump which caused the thing to leak with every downstroke and I have a feeling Ill be cleaning it up for a while yet! After replacing the O-ring, I lifted the top without sufficient fluid so midway up, I added more fluid and the stroke was still very soft although I was able to get the top up after pumping 50+ more times. After dropping the top, I began pumping and the result was pretty solid, but still a bit soft. I thought through the pumping mechanism and realized that the "cheater bar" hits the floor before the pump maxes out in the downward stroke. If there is air in the "pumping cylinder," It will remain there until the pump is completely maxed out to purge the air then draw in hydraulic oil on the upstroke. What I did to purge the air is put the lever in the position to lower the camper, then, without the cheater bar, give the pump a few strokes making sure to push it all of the way down and pull all of the way up again. Finally, I switched the knob to the raise position and began pumping. Immediately, the full stroke is solid all of the way to the top.
I replaced all of the O-rings and seals on my pump twice and it resulted in no leaking but weak pumping action. I think having air in the cylinder was my problem and may help others with the same problem. We were looking at replacing the pump entirely, but now it works good as new.
I hope this helps other Alaskan owners out there! Cheers!