Troubleshooting your Karcher gas pressure washer when it produces weak spray
An insufficient water supply can cause low pressure at the nozzle. Check the water pressure at the source and the flow connected to the inlet of the pressure washer. Check the inlet screen for a clog that could be blocking inlet water flow.
Check whether a low-pressure spray tip is installed on the wand; if so, install a different nozzle. A problem with the wand or pressure hose can also cause low nozzle pressure. Clean or replace the wand if necessary. Replace the pressure hose if it's clogged.
A pump failure can cause low nozzle pressure. Replace the pump check valves or replace the entire pump if it doesn't build up adequate spray pressure. A stuck unloader valve can also cause low pressure at the nozzle. Replace the unloader valve if it sticks open and constantly recirculates water back to the pump inlet.
What to do when the engine won't start on your Karcher gas pressure washer
When the engine doesn't start, first make sure the rocker switch that controls the engine is in the On position. Next, check the fuel; the engine won't start if the engine is out of fuel or if the fuel is stale or contaminated with water. Replace the fuel in the gas tank if the fuel is older than 3 months.
Bad fuel can contaminate the carburetor. Clean or replace the carburetor if it's gummed up from using stale fuel.
The engine may also need a good tune-up so it will start easily. A tune-up includes changing the oil, changing the spark plug, replacing the air filter, checking the ignition system and adjusting the throttle and choke controls.
A bad recoil starter can prevent the engine from starting. If the engine doesn't spin when you pull the starter rope, you'll likely need to replace the recoil starter.