Thanks Jamie. Pirtek found some seals for the pump but they are not exact and nla from Volvo as a repair kit so I have to do some modifications on the old pump to get it working. the Volvo Dude started telling me that ir relies on a "relief valve" of sorts built into the hand pump underneath the plunger not just the seals. I am not convinced, but hey my expertise is computers.
I have the old pump mostly apart except for the plunger barrel, which somebody has previously "dismantled with a pipe wrench" and I will hopefully get apart to see if he is right.
I got home last night and thought OK, he has got it working and I can continue from here... not to be! He had left the cab sitting at about 30 degrees to see if it dropped (which it hadn't) so I though cool I'll tilt it fully so I can safely work on the engine. Pump away and get 2/3 of the way there and then pump runs out of oil. Add oil and keep pumping until cab gets over the hump and starts lowering all the way on its own, sucking in more air. So then I think ok, lets try puttin git back down. Pump away and it heads back, keep pumping and all is good except the oil I added all ends up on the ground under the pump. So I reverse the valve again and pump as fast as I might I can't get the cab to move up. Basically back to square and no doubt charged for a callout. I have to ask, are theer two sizes of pump reservoirs for these??? I just can't see that it is big enough to hold all the oil from the stroke of the ram, even taking into account the return oil to the other side (which is much smaller as the rod takes up most of the volume). I just dunno now. New pump $750 which would be fine if it were definitely the problem and we could return the other one.
Thanks for the tips Mammoth.
BTW, the air system seems to have settled down. Maybe I was just being impatient, or draining the wet tank and making it work a little has cleared the breech....