April 1, 2013

How to replace a pressure washer unloader valve

By Lyle Weischwill
How to replace a pressure washer unloader valve

This step-by-step repair guide explains how to replace a pressure washer unloader valve.

When you let go of the trigger on the wand, the unloader valve opens to recirculate pressurized water to the pump, so the water won't overhead and damage the pump.

Common symptoms that indicate you need to replace the pressure washer unloader valve include:

  • The thermal release valve opens and sprays steam water from the pump. This happens when the unloader valve clogs or sticks shut.

  • Nozzle water pressure decreases quickly after you press the wand trigger. This symptom occurs when the unloader valve sticks open.

  • The engine stalls when you're not using the wand. When pressure builds up in the pump because the unloader valve isn't opening as it should, the engine can't continue to turn the pump shaft so the engine dies.

If the pressure washer unloader valve isn’t working, replace it using the manufacturer-approved gas pressure washer part. The unloader valve kit includes the O-ring and all parts needed for the repair.

Follow these steps to replace a Briggs & Stratton, Husqvarna, Troybilt, Snapper or Craftsman pressure washer unloader valve.

Quick links
Tools required
Wrench set
Silicone lubricant
Torque wrench (optional)
Work gloves
Repair difficulty
Time required
15 minutes or less
Repair difficulty
Time required
15 minutes or less

Instructions

  1. 01.

    Disconnect the spark plug

    Pull the spark plug wire off the spark plug on the pressure washer engine.

  2. 02.

    Remove the unloader valve

    Use an open-end wrench to turn the unloader valve counter-clockwise to remove.

    PHOTO: Loosen the unloader valve.

    PHOTO: Loosen the unloader valve.

    PHOTO: Remove the unloader valve.

    PHOTO: Remove the unloader valve.

  3. 03.

    Install the new unloader valve

    Install the O-ring from the kit on the new unloader valve.

    Lubricate the O-ring on the new unloader valve with silicone lubricant.

    Thread the new unloader valve into the pump and tighten.

    Tip: : If you have a torque wrench, tighten the new unloader valve 10-12 ft.-lbs.
    PHOTO: Install the new unloader valve.

    PHOTO: Install the new unloader valve.

  4. 04.

    Reconnect the spark plug

    Reconnect the spark plug wire to the engine.

  5. 05.

    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.

Warning: Undertaking repairs to appliances can be hazardous. Use the proper tools and safety equipment noted in the guide and follow all instructions. Do not proceed until you are confident that you understand all of the steps and are capable of completing the repair. Some repairs should only be performed by a qualified technician.

Symptoms for gas pressure washers

Choose a symptom to see related pressure washer repairs.

Main causes: stale fuel, gummed up carburetor, engine needs tune up, throttle and choke controls need adjustment, bad recoil starter
Main causes: faulty unloader valve, bad pressure regulator
Main causes: broken recoil spring, damaged recoil starter
Things to do: tune up the engine, inject pump saver into the water pump when storing the pressure washer for the winter
Main causes: overfilling engine with oil, improper fuel/air mixture, choke system problems, dirty carburetor, engine needs tune up
Main causes: pump running for more than 5 minutes when the spray wand isn't being used, faulty pressure relief valve, bad unloader valve
Main causes: insufficient water supply, clogged water inlet screen, clogged pressure hose, faulty pump check valves, stuck unloader valve
Main causes: using a high-pressure spray tip when applying detergent, clogged siphon tube, chemical injection system failure
Main causes: dirty air filter, stale fuel, clogged or dirty carburetor, bad unloader valve

Repair guides for gas pressure washers

These step-by-step repair guides will help you safely fix what’s broken on your pressure washer.

How to install a pressure washer chemical injection kit

The chemical injection valve draws detergent into the pump. If it’s not drawing detergent, use a repair kit to replace the chemical injection valve.

Repair difficulty
Time required
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April 1, 2013
By Lyle Weischwill
How to install a pressure washer O-ring kit

O-rings seal fittings on the pressure washer pump. Damaged seals allow water to leak from the pump. Follow these steps to replace the O-rings in a leaking pressure washer pump.

Repair difficulty
Time required
 45 minutes or less
April 1, 2013
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How to replace a pressure washer pump

The pump can be damaged by air in the inlet water supply or by chemicals that remain in the pump body after using the chemical injection system. Follow these steps to replace a damaged pump.

Repair difficulty
Time required
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