Skip to Content

Pressure Washer Won’t Start or Stay Running

Pressure washers are extremely useful tools that make cleaning tough stains fast and easy. It’s a handy weapon to have in your arsenal against dirt and grime. While it’s nice to have a pressure washer in your garage so you can grab it and go whenever it’s needed, sometimes you pull it out and find that your pressure washer won’t start, won’t crank, or won’t stay running.

If your pressure washer won’t start, a common cause is old or contaminated fuel. Stale fuel can clog the carburetor and prevent the engine from firing. To resolve this, empty the fuel tank, clean the carburetor, and refill with fresh gasoline.

Pressure Washer Won't Start or Stay Running

Another potential reason for a pressure washer not starting is a faulty spark plug. Over time, spark plugs can become dirty, corroded, or worn out, affecting the engine’s ability to start. Remove the spark plug, inspect it for damages, clean it, or replace it with a new one if necessary.

Additionally, the pressure washer might have a clogged air filter, which can restrict airflow to the engine and prevent it from starting. To check this, locate the air filter, remove it, and inspect for dirt and debris. Clean the air filter or replace it if it’s excessively dirty. Ensuring a clean and clear air filter can often restore the washer’s functionality.

Pressure Washer Won’t Stay Running

If your pressure washer starts but won’t stay running, a frequent issue is water starvation. Ensure the water source provides an adequate flow and that there are no kinks or blockages in the hose. Connect the hose securely, turn on the water source fully, and ensure it meets the washer’s required flow rate.

Another common reason for a pressure washer to stall or shut off is a clogged or dirty carburetor. Residue from stale fuel or debris can accumulate over time, affecting the machine’s performance. To address this, clean the carburetor or consider adding a carburetor cleaner to the fuel to break down any deposits.

Additionally, a malfunctioning unloader valve can cause the pressure washer to not maintain its operation. The unloader valve’s function is to redirect water flow when the trigger isn’t engaged. If it’s faulty, it can affect the pressure balance, causing the machine to shut off. Inspect the unloader valve, adjust its setting, or replace it if necessary to ensure proper function.

What to Look for and How to Start It

What to Look for and How to Start It When Your Pressure Washer Won't Start

When troubleshooting your pressure washer, it would be helpful to be able to eliminate some things right out of the gate. Luckily, depending on what condition you find your machine, you can focus your search on certain potential problems.

If the pressure washer has been sitting for a long time, for example, the fuel could have broken down and clogged the carburetor. If it won’t fire, it could be the spark plug or ignition coil. If it starts up fine but won’t stay running, it could not be getting the proper ratio of gas and air due to clogged filters. Knowing what to look for will save a lot of time.

Start by Checking the Basics

Before checking on specific problem areas, start by making sure you aren’t overlooking something extremely basic.

Make sure:

  • Pressure washer is plugged in (if electric) or has enough fresh gasoline (if gas powered)
  • Turned on
  • Properly connected to a water source (that is turned on)
  • There are no kinks or leaks in the hose

Only when you are sure you aren’t overlooking something basic can you begin to investigate specific failures that could cause your pressure washer to not start, crank, or stay running.

Winterize a Pressure Washer

Gas powered pressure washers have an engine that powers the pump. Like other tools whose engines sit idle all winter (such as your lawn mower) it needs to be properly winterized in order to avoid damage during the cold months.

Winterizing a pressure washer includes making sure all of the tanks and hoses are fully drained of water and detergents. When what freezes it expands. Any water left in your pressure washer could expand enough to damage the internal component of the pump, hose, or tanks.

Fuel should also be drained from your gas-powered pressure washer before storing it in your garage over the winter. Not only is there the risk of expansion, but gasoline breaks down over the course of months in storage. Gasoline can separate into its component ingredient. When the less viscous liquids evaporate, what is left is a thick tar that can clog your washer’s carburetor.

Check the Washer’s Spark Plug

Inspecting your pressure washer’s sparks plugs is always a good place to start because they are easy to inspect and cheap and easy to replace if they are the problem. Locate and disconnect the terminals from the spark plug.

Often, a visual inspection is enough to determine if the spark plug is the problem. With your naked eye you can see if:

  • The porcelain insulator is damaged
  • The electrode has heavy carbon buildup on it or is in disrepair

If any of these exist, simply put in a spark plug.

Even if the spark plug appears to be fine, it could still be defective. There are special tools that can test to see if a spark plug is working. When the engine is cranking, you should see a strong spark between the tester’s terminals. If there is no spark, replace the spark plug. If there is a spark, the spark plug is working fine. Check that all of the connections are secured in place.

Check the Ignition Coil

If the spark plug is working, the problem could be the ignition coil, which sends voltage to the spark plug while the engine is running. A defective ignition coil could prevent the pressure washer from starting.

The ignition coil can be tested with an ignition coil tester. If it is defective, it needs to be replaced. If the spark plug and the ignition coil are both operating properly, the problem is elsewhere.

Check the Carburetor

If your pressure washer won’t start after winter, there’s a good chance the problem could be that fuel was left in the engine. Over time, gasoline can separate and some of the components can evaporate, leaving behind a thick, sticky substance that can clog the carburetor, which in turn can cause the engine to not start.

If this is the problem, you may be able to clean the carburetor with a carburetor cleaner which is specially designed to break down this sludge. If this does not work, you may have to rebuild or even replace the entire carburetor.

Even if the fuel hasn’t clogged the carburetor, it could still be too old. While it takes a few months for gasoline to become a thick, sticky tar, it begins to break down and become less effective after only one month. When possible, you shouldn’t use gas that is more than 30 days old.

Checking the Washer When the Water is On

Checking the Washer When the Water is On

Your pressure washer has a pump that forces water from your water into a tank, thereby creating the water pressure that you will use to clean surfaces. Some pumps will not start unless they are primed, meaning that the hoses are filled with water with no air pockets. In some cases, air in the hose will prevent the pressure washer from starting.

Check That the Pump is Primed

You’ll want to make sure that you pump is primed. Here are a few steps is you need to prime the pump.

  1. Start by connecting your garden hose to the pressure washer and turning on the water.
  2. Connect your high-pressure hose and wand.
  3. Pull the trigger on the wand to allow trapped air to escape.
  4. With the water running, hold the wand’s trigger open with one hand (pointed in a safe direction) while you start the engine.

This should allow the air pressure to release from the hose, allowing the engine to start.

When you are done using your pressure washer, remember that the tank and hose are still filled with high pressure water. You will need to release it. Here are the steps.

  1. Turn the engine on and then turn off and disconnect the garden hose.
  2. Hold the trigger on the wand down to release pressure.
  3. Disconnect the wand and high-pressure hose and drain the water out before storing.

Checking the Washer After it Has Out of Gas

Checking the Washer After it Has Out of Gas

Perhaps your pressure washer was working perfectly fine. You removed the stain from the driveway cement, cleared the grime from the siding, and was about to clean the patio furniture when you ran out of gas. It should be a simple fix, right? Put in more gas, start it up, and continue as you were. After you refill the tank, however, the pressure washer won’t start. What gives?

Check the Fuel Pump

Many things can go wrong when you run your pressure washer’s tank out of gas, which can cause it not to start back up when you put gas in it. The final dregs of fuel could be old and dirty and clog the carburetor, for example, and you would have to clean or replace or rebuild the carburetor.

Some fuel pumps are cooled by the gas that flows through them. When the pressure washer runs out of gas, then, the fuel pump overheats and needs to be replaced.

You can try to get the pressure washer started again by removing the spark plug, putting about a tablespoon of gasoline or lighter fluid in the socket, replacing and reattaching the spark plug, and trying to start it. Sometimes wetting the bowl in this way is enough to start it up again after the fuel pump has burned dry.

Checking the Washer After it Has Been Sitting for a While

Checking the Washer After it Has Been Sitting for a While

It’s always hard to do something you haven’t done in a while This is as true for pressure washers as it is for people. Just as you would have a hard time taking a quiz on algebra or state capitals, your pressure washer might not start after sitting for too long.

Try a Tune Up

You’ll want to do a complete tune up to see what the problem is. To do this you’ll need to:

  • Make sure the fuel and air filters are clean.
  • Test the spark plug and ignition coil.
  • Check the flywheel key.
  • Check for any leaks or visible damage

A sitting pressure washer is prone to all kinds of wear and tear.

Check the Carburetor

If the pressure washer has been sitting for a while, you’ll want to take extra care to check the carburetor. If fuel was left in the engine, it could have deteriorated over time. As gasoline separates, come components evaporate away, leaving a thick, sticky goo that can clog the carburetor.

If this is the problem, you may be able to clear the blockage with a carburetor cleaner (but don’t use this if the carburetor’s needle valve tip is rubber as this would corrode the valve). If not, you may need to rebuild or even replace the carburetor.

Checking the Washer When it Gets Too Hot

Checking the Washer When it Gets Too Hot

Another frustrating problem you may have is that your pressure washer starts fine when cold, and works for a while, but if you need to stop for some reason, the engine will not start again while it is still warm. If you wait a while until the unit cools off it starts up again. This can be frustrating and waste a lot of your time if you are trying to get a job done.

Check the Carburetor Screw Settings

The pressure washer engine’s carburetor is responsible for mixing fuel and air at the proper ratio in order for the engine to run properly. If there is too much fuel and not enough air, the fuel won’t burn because combustion requires oxygen. If there is too much air and not enough fuel the engine will not run because there isn’t enough fuel to burn and the air will essentially blow it out.

In addition to being clogged by sticky, old fuel remnants, the carburetor could be adjusted to improper settings. The balance is so delicate that it is possible that the engine starts fine when the engine is cool, but when the engine has been running for a while the parts are hot, the metal parts expand, and this is enough to throw off the ratio enough that the washer won’t start.

You can adjust the settings of your pressure washer’s engine’s carburetor’s mixture screws. These screws are very sensitive and turning them by even a quarter of a revolution can have dramatic effects. Finding the correct balance is a long process of trial and error, but it could save you hundreds or even thousands of dollars if it means not having to replace the entire washer.

Check the Exhaust Valve

It could also be that when the engine is hot, the metal expands enough that the exhaust valve gets stuck open. This seems to be pretty rare and hard to diagnose. Replacing the exhaust valve may solve the problem.

Checking Washer After it Has Been in Storage For a While

Checking Washer After it Has Been in Storage For a While

Any time your pressure washer has been in storage for a long time, you may need to do a tune up to get it started again.

Copyright protected content owner: and was initially posted on May 17, 2020.

If your pressure washer won’t start after it has been in storage, there are many things that can be wrong. Like other pieces of machinery (as well as your own body), your pressure washer works best when used regularly. If it sits for too long, it can get figuratively (and literally) rusty.

Try a Tune Up

Make sure everything is in working order. Test the spark plugs and ignition coil. Wash or replace the fuel and air filters. Make sure it’s filled with fresh gas and oil. It may take a thorough look over to find the problem.

Check the Carburetor

Any time a pressure washer is in storage, it should be drained of all fuel. After a few months the gasoline can separate, evaporate, and turn into a thick, sticky sludge that can clog the carburetor. If this has happened, it will need to be cleaned, rebuilt, or replaced.

Checking the Washer After it Has Been Running

Checking the Washer After it Has Been Running

What could be more frustrating than using your pressure washer and having it suddenly stop working suddenly. If you pushed your washer to the edge of what it can handle, only to have it instantly fail on you, the solution could be easier than you think.

Check the Flywheel Key

The flywheel key is a small piece of metal that engages the flywheel and fits inside the crankshaft. It is designed to shear in half if the pressure within the crankshaft is too great due to some sort of overexertion. Because it is actually designed to break in this way, it is simple enough to simply replace the flywheel key to get the pressure washer working again.

Copyright article owner is for this article. This post was first published on May 17, 2020.

Checking When Washer Won’t Stay Running

Checking When Washer Won't Stay Running

If you pressure washer starts up easily enough but won’t continue running so that you can actually use it, there are a whole different set of potential problems to check for.

Check the Fuel Cap

As the pressure washer runs, fuel from the gas tank is passed through the carburetor and burned in the engine to power the pump. As gas leaves the tank, air must be allowed to vent in through the fuel cap to fill the increasing amount of empty space. If the fuel cap is clogged, air cannot vent in, pressure builds, and a vapor lock prevents gas from moving to the engine.

Therefore, if the fuel cap vent is clogged, gas won’t get to the engine, and the engine will stall out. To test if this is the problem, try running your pressure washer with the fuel cap slightly unscrewed, allowing air to seep in. If this keeps the engine running, clean or replace the fuel cap so it can vent properly.

Check the Fuel Filter

We’ve already discussed how old gas can evaporate and form a sticky, thick sludge that can clog the pressure washer’s carburetor. To prevent this, the fuel must pass through a fuel filter. Even if the fuel filter succeeded in stopping this tar from reaching the carburetor, it can itself become clogged. Make sure the fuel filter is clean or replace it.

Check the Air Filter

The carburetor mixes fuel and air in order to keep the engine running. The air filter keeps debris out of this mix but can become so clogged that not enough air gets through, causing the engine to stall. Make sure the air filter is clean or replace it.

ReadyToDIY is the owner of this article. This post was published on May 17, 2020.

Check the Spark Arrestor

Your pressure washer’s engine may have a spark arrestor, which is a small screen that prevents the engine from emitting sparks. Like the fuel and air filters, it must not be clogged in order to work properly. If it is, clean it with a wire brush or replace it.