Does anyone know the internal workings of such things?
I have a decent quality brass-bodied spray gun - the type with a dial on the front for selecting one of 10 spray patterns. It won't turn off. At first I could turn off by tapping the protruding end of the valve mechanism where it meets the handle, but pushing it now results in a spray of water backwards, and still no turn off. I suspect an internal washer has deteriorated and is making the mechanism stick and also allowing water backwards.
I have tried oiling every orifice to no effect. When I tried to dismantle it I was defeated at a circular white plastic part under the dial, which appeared to be held on with two screws but would not shift when they were removed, so it's glued, wedged or gunged in.
Any suggestions short of replacing?