I had same problem, very common. Can be several problems. See manual trubleshooting, can get from Karcher online for free. My problem was caused by a tiny piece of sand stuck in the nozzle. Easy fix- remove six star head screws and separater plastic covers. Then pull out the plastic nozzle. The plastic nozzle is two pieces that can be further separated if needed. Take a SMALL pin and clear the obstruction. My sand was clear as glass and so was hard to see, but pin pushed it out. Wash it out so it dosn't get stuck in there again; reassemble. Also, water intake does have a filter (again, see manaual). Pull out hose washer, then pull out filter with neddle nose pliers.
E Beck
May 2010