Pressure Washer Dies at Full Throttle: Why and What to Do About It

You know the feeling: you are right in the middle of a cleaning job, and the pressure washer just dies on you at full throttle. You have not finished, and you just want to get the job completed. Thankfully, it is easy to remedy this.

To fix a pressure washer that dies at full throttle, you should make sure that there’s no problem with the fuel system, specifically the carburetor, fuel cap, and fuel filter. You should also clean the spark arrestor and the unloader valve.

Read on and find out why these parts may be the source of your frustration, and more importantly, how to fix or replace them.

Check to See if Your Pressure Washer Starts Up and Then Fails After a Few Minutes

1. When your pressure washer dies on you while in the middle of operating it, turn it off and start it again, if it starts and then stops after a few minutes, it might be the carburetor that’s causing the trouble.
2. Check if your pressure washer has a clogged carburetor, which is caused by fuel that has partially evaporated. The fuel becomes sticky, and the thicker residue can clog the carburetor.
3. To clean your carburetor, you will need to access it by opening and taking out the air filter box, the throttle cover, and the intake. You will also need to disconnect the gas line that you see running between the fuel tank and carburetor. 
4. Open the carburetor and throw away the fuel that you see there. You should also check for corrosion and rust, which means that you will need to replace it with a new one.
5. If it’s only dirty, you must take the carburetor apart and then clean the carb bowl.

You can follow this video if you want to check, clean, or replace a clogged carburetor:

Cleaning a small engine carburetor. Briggs and Stratton. Bad gas. Ethanol problems.

Related Reading: Pressure Washer Shuts Off After a Few Minutes: Primary Causes

Other Tips When Dealing With a Clogged Carburetor

If you are dealing with a clogged carburetor, here are some tips that can help you immensely:

• You can use this WD-40 Throttle Cleaner (link to Amazon) to help you unclog a carburetor easily.
• If this is your first time to deal with a small engine, you can buy a carburetor repair kit so that you would have everything you need to access and repair your carburetor.
• While you’re cleaning the clogged carburetor, you should also inspect the jets to see if there are no obstructions. You will need to rinse all of these parts and then dry them with compressed air.  
• Clean the other parts with soapy water and see if there are gaskets that need replacement.
• You can avoid this problem by using only fresh fuel. If you are not using your pressure washer for a long time, buy a fuel stabilizer like STA-BIL (22214) Storage Fuel Stabilizer (link to Amazon) to help keep the gasoline fresh in the tank for up to two years.

Check the Unloader Valve

When your pressure washer stalls and then dies after it sprays water, then it might be a problem with the unloader valve.

This part keeps the pressure under control when your pressure washer is idling. A problematic unloading valve will cause damage to your pressure washer, or it will deliver very low water pressure.

To clean the unloader valve, get your screwdriver and wrench, and then keep some grease and alcohol handy. Then do the following:

1. Unplug the unloader valve from the bay by taking out the U-shaped retaining pin.
2. Inspect the piston to make sure that it can move freely. This component is responsible for controlling the pressure retention. If the piston is restricted in any way, your pressure washer will stall and die. If it does not move freely, unplug the piston and the spring and clean it with alcohol. You should also lubricate the piston and the spring using silicone grease (link to Amazon).
3. If that’s not the problem, check if the O-rings of the unloader valve are in good condition. If not, your unloader valve may not work properly and can cause your pressure washer to shut down. Replace the O-rings with similar sized ones from this Tool Daily Pressure Washer O-Rings Kit (link to Amazon).

This video will show you where the piston is, what the unloader valve looks like, and how to remove and put it back into place:

Fix Pressure Washer Unloader Valve in 2 Minutes

Aside from the piston and the O-rings that you find on the unloader valve, the settings might be too high. If your unloader valve fails to open up, it will not be able to cycle the water back into the inlet.

This can stall the engine of your pressure washer. As such, you will need to adjust the settings if needed.

Make Sure the Engine Is Getting Enough Gas

If your pressure washer suddenly gives up at full throttle, the engine might not be getting enough fuel to keep going. Here are some things that you can do:

Replace a Clogged Fuel Cap

If your pressure washer dies at full throttle, it may be because of a clogged fuel cap. When you run your pressure washer, the gasoline is used up to the point that the level in the fuel tank is not enough to keep your equipment running.

The fuel cap brings air into the fuel tank so that the level rises, and your pressure washer continues working. If this part is clogged, no air will get inside the tank, causing a vapor lock that stops the flow of fuel.

To check if your pressure washer’s fuel cap is clogged, you can loosen it and then start the engine. If it does not die even at full throttle, then you will have to replace the fuel cap.

Replace a Clogged Fuel Filter

Like a carburetor, fuel filters can also get clogged by partially evaporated gasoline that has become sticky. A clogged filter may prevent fuel from reaching the carburetor and stall the engine.

This video will show you how to access and then replace a clogged fuel filter.

How to Change Your Mower's Fuel Filter

Clean a Dirty Air Filter

A dirty air filter will block the air that enters the carburetor, which in turn will stall the engine. The air filter prevents dirt, debris, and dust from getting into the carburetor and engine.

Do not operate your pressure washer without it in place, or your pressure washer will not last that long.

You can clean an air filter when it is dirty, just remember not to twist it too much. You will also need a high flash point solvent such as paint thinner to wash it.

This video will demonstrate how to access the air filter, what it looks like, and how to replace it:

Pressure Washer Air Filter Cleaning

Looking for a Quick Fix? Use Sea Foam

If it is gummy fuel that’s causing your pressure washer to stop while at full throttle, then a quick but temporary fix is to spray using a motor treatment like Sea Foam (link to Amazon).

Here’s how much Sea Foam you need to add to the fuel to get the engine run:

How much Sea Foam should I add to fuel?

Clean the Spark Arrestor

A spark arrestor stops the pressure washer’s engine from creating sparks. If it is clogged with oil, soot, or carbon, the engine might stall.

The spark arrestor screen is found in the engine’s muffler, and you will need to open this to get to the spark arrestor assembly.

When you get the screen out and confirm that it does need cleaning, you will need to use a torch like this Fun Owlet Butane Torch Kitchen Blow Lighter (link to Amazon) to burn the clogged oil from the screen.

Here’s a video that shows you how you do that:

How to Clean a Spark Arrestor Screen on a Small 2-Cycle Engine--A Quick Fix

Conclusion

Fortunately, it is very easy to fix a pressure washer after it dies in full throttle. You just need to make sure that the engine is getting enough gas and that the usual suspects are clean or in good condition.