Eddie, I've answered this in a similar question.
If it runs but there is only token water pressure the most likely cause is a small piece of debris in one of the valves in the cylinder head.
Go to a spares site like espares.co.uk , select your machine, select cylinder head from the left side parts page and get an exploded view.
If you are competant to strip it, look at the diagram for the little valves etc and carefully strip/clean/rebuild each sub assembly as you go.
The smallest piece under a seat will stop the pressure build up. Also check for damaged o rings/seals.
You will need a Torx screwdriver, usually T 15 to separate the machine halves.
Parts are readily available but keep a cool head on the prices against the cost of a new machine?
Lastly, I assume you are running from a cold tap, not hot? Must be cold.
t.r.services, July 2009