water pouring out of handle of champion cpw1900?

Have just (today) had same fault, when using machine after long spell not used. Unscrewed all the crosshead screws of the trigger part of the pressure lance and prised off its cover, exposing the orange on/off lever,
in its position touching the plastic piston part of the water pressure inlet assembly. I noticed a small bit of green plastic jammed between the piston and its barrel, restricting the pistons movement to its off position, thus letting water leak out of the casing.
Disengaging the pressure inlet hose/piston assembly
away from the orange lever was easily done by lifting the hose entry end, clear from its laid down position between two of the hold down screw holes,...at the same time (three more actions required here) rotating it clockwise to miss the lever, whilst rocking it as I pulled gently towards me. This had the effect of releasing the piston from its barrel..(watch out for a compression `piston return spring` at this stage, to drop away from the plastic peg it sits on).
Lastly, my findings were, that the green plastic was the edge of a green `o` seal slightly damaged, still mostly sat in its piston groove, but stopping the piston being returned to its off position.
I hope this helps should you have the same fault......
but tomorrow, my search around Bristol starts for a
replacement `o` seal !

Brian
July 2011