Firstly, check the nozzle – assuming that is correct and you still have no or low pressure the golden rule is to connect the pump to the mains water supply – whichever machine you are testing start with a good mains feed.
1. With the gun and lance connected turn the tap on – can you see a leak? If so there is your problem, if water can leak out air can get in and the pump won’t produce pressure – simple as that. (Leaks from underneath the pump are either worn seals or a cracked piston – strip to find out which.)
Remedy: Fix leak or replace seals or piston.
2. Check enough flow of water can get into the pump. Make sure all the filters are clean. The new Tempest hot water machines have a fine filter which will remove most solids. All Demon machines are now double filtered. Have you checked both of them?
Remedy: Strip and inspect filters.
3. There are no leak’s what next? With the pump switched off pull the trigger, water will spray out. Keeping the trigger pulled switch the pump on, if the water spray does not improve the valves are the fault. Either worn out or dirty. Strip and inspect. (The high pressure hose will also vibrate on the ground.)
Remedy: Replace or clean valves.
4. The valves are OK there are no leaks but it still won’t get up to pressure – what next? The unloader valve piston and seat are damaged or worn allowing some of the water to circulate around the cylinder head – strip and inspect, you will see any damage.
Remedy: Strip unloader and inspect – replace damaged parts.