In reply to Alex Purser:
This the thing?
http://stovecollector.tripod.com/cs_hvstd210.htm
If so then there is a small screw on top of the filler cap to release the pressure when you have finished cooking.
Unscrew the pump and see if it is dried out, if so apply some vaseline or similar to it, you may need a new washer if it is cracked. The makers still probably make them to fit, why change a proven design?
Fill the tank to 3/4 capacity with paraffin, put lid on but do not screw up pressure relief valve yet.
Put some meths or burning paste in the cup round the burner to preheat it, when it is nearly spent, close the pressure valve and give a a FEW pumps to see if it will fire up. If so, give another three or four pumps and leave for half a minute then pump till you have a fierce enough flame to boil water.
If it is too cold the stove will flare up, just release the valve and wait for it to warm up more.
And THAT is how it was in youir daddies day;-0