Trust the Pressure Washer Repair Experts

When your pressure washer isn't getting the job done—maybe the engine won't start or it's not spraying correctly—Sears Home Services has the troubleshooting advice to help you diagnose the problem.

When you can’t fix the problem yourself, visit our ServiceLive website and have a local service provider near you fix the problem.

Use these DIY troubleshooting tips to fix basic problems that you experience with your pressure washer.

Why does water spray out of my pressure washer's pressure relief valve?

If the pressure washer runs for more than 5 minutes when the spray wand isn't in use, the water in the pump often overheats, causing the thermal relief valve to open and discharge hot water onto the ground. When the thermal relief valve opens, cool water enters the pump and cools the system. Once the pump has cooled, the thermal relief valve closes and the pressure washer operates normally.

The unloader valve reduces water pressure within the pressure washer pump when the pump runs but the spray wand isn't used, by recirculating water to the pump inlet. If the valve sticks in the closed position, the thermal relief valve frequently discharges hot water onto the ground because the unloader valve can't open to allow recirculation. You’ll likely need to replace the unloader valve if it sticks shut and causes the thermal relief valve to open frequently.

Follow these steps to replace the unloader valve.

1. Wear work gloves to protect your hands.
2. Disconnect the wire from the engine’s spark plug.
3. Use a wrench to turn the unloader valve counter-clockwise and remove it.
4. Install the O-ring from the kit on the new unloader valve.
5. Lubricate the O-ring on the new unloader valve with silicone lubricant.
6. Thread the new unloader valve into the pump and tighten.
7. Reconnect the spark plug wire to the engine.

Check pressure washer operation. Start the pressure washer and check for water leaks at the new unloader valve. Make sure that the new unloader valve works properly so that the emergency relief valve doesn’t open frequently and that the wand gets proper water pressure.

Why won't my pressure washer engine start?

When the engine on your pressure washer won't start, follow these troubleshooting tips to fix the problem:

• Make sure the rocker switch that controls the engine is in the On position.

• 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 6 months. Add fuel stabilizer to gasoline to help keep the fuel fresh.

• Stale fuel or debris can contaminate the carburetor. Clean or replace the carburetor if it's gummed up from using stale fuel and your power washer won't start.

• The engine on a power washer that won't start 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.
  If you still can’t get the pressure washer engine started after following these DIY troubleshooting tips, have the pressure washer serviced by a technician.

Why is the spray from my pressure washer weak?

An insufficient water supply can cause low pressure at the pressure washer's 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.

How to Replace Pressure Washer Pump Check Valves

Pressure washer check valves let enough water flow through the pump and manifold to pressurize the water at the nozzle. If the pressure washer check valves are damaged, the pump won’t build pressure. Air in the inlet water supply can damage the pressure washer check valves, as can chemical residue left in the pump. Replace damaged check valves by following these steps.

1. Disconnect the spark plug wire from the spark plug. Remove the gas cap. To prevent fuel from leaking from the tank when you tip the pressure washer over to access the pump, place a plastic bag over the mouth of the tank and then reinstall the gas cap.
2. Remove the inlet water hose and the outlet nozzle hose connection from the pump.
3. Use a wrench to remove the caps from the check valves on the side of the pump manifold. Be prepared for water to spill from the manifold when you remove the check valve caps.
4. Insert a sheet metal screw into the plastic body of the check valve and screw it down so it grips the check valve body, and then pull the screw and check valve body out of the pump. Use a mechanic’s pick to remove any residue left by the valve body or seals out of the pump body. Repeat the process to remove all the check valves.
5. Install the new check valves into the body of the pump. Press the check valves down so that they seat properly.
6. Reinstall the check valve caps on the pump manifold. Place a small amount of thread-locking adhesive on the check valve cap threads when reinstalling the caps. Tighten the check valve caps securely with a wrench.
7. Tip the pressure washer to access the bottom of the pump. Remove the 3 Allen-head screws that secure the manifold to the pump. Pull the manifold off of the pump. Set the manifold down on a stable work surface.
8. Remove the water seals from the top of the check valves. Insert a sheet metal screw into the plastic body of the check valve and screw it down so that it grips the check valve body. Pull the screw and check valve body out of the pump. Use a mechanic’s pick to remove any residue left by the valve body or seals out of the pump body. Repeat the process to remove all of the check valves.
9. Install the new check valves into the body of the pump. Press the check valves down so that they seat properly. Install the water seals at the top of the check valves.
10. Reinstall the pump manifold and tilt the pressure washer upright. Remove the plastic bag from under the gas cap and reconnect the spark plug wire.

Replacing the check valves should restore proper water pressure to the wand.

For more DIY pressure washer repair advice, visit our Pressure Washer Repair Help page.