Why Does Pressure Washer Loses Pressure and Dies When Trigger Is Pulled?
There are many reasons to make your pressure washer keeps shutting off when you start washing but we will mention the most common cause to let you know the overview of the problem.
The premature death of the pressure washer when pulling the trigger is mainly related to the following parts: the unloader valve, o-ring, and pressure washer trigger. In which the main cause is usually a problem with the unloader valve.
1. Faulty Unloader Valve
Most pressure washer problems stem from the unloader valve. This valve controls the pressure by letting high-pressure water flow out the nozzle when you squeeze the trigger. When you release the trigger, it redirects the water back in a loop to keep the pressure up. The engine cuts off when the pump pressure gets higher than the engine can handle. Common unloader valve issues are cracked o-rings, grit building up in the spring, and a stuck shaft.
2. Old O-Rings
What's likely happening is the O-rings that seal the oil pump are failing or deteriorating. When that happens, oil starts to leak past those O-rings. That oil leak prevents the unloader valve from functioning properly, so when you squeeze the trigger to let water through the nozzle, the pressure washer cuts off because it doesn't sense enough pressure to stay running. Deteriorating O-rings in the oil pump are a common cause of this issue, allowing oil to escape and messing with how the unloader valve senses the pressure.
3. Problem with the Pressure Washer Trigger
Even if you fix issues with the unloader valve and oil pump O-rings, the trigger itself could still be the root problem causing your pressure washer to shut off when you squeeze it.
If switching to a different trigger works, then there's likely an issue with your current trigger. Take the trigger apart to see if you can identify an obvious problem.
4. Erroneous Setting
The issue is that when the unloader valve is set to a high-pressure setting, it can't properly divert water back into the intake loop when you release the trigger. This means pressure keeps building up inside the pressure washer instead of being relieved. The rising pressure eventually causes the machine to stop running altogether.
Basically, the unloader valve needs to be set to a level where it can actually do its job of unloading excess pressure by sending water back to the intake – but at higher settings, it can't handle that function properly.
How to Solve A Pressure Washer That Dies When The Trigger Is Pulled
Step 1: Locate the unloader valve, which is usually above the pump and has a black handle. Remove the retaining pin, which is a U-shaped metal pin, using a screwdriver. This will disconnect the unloader valve.
Step 2: Remove the piston from the unloader valve by loosening the nut that secures it with a screwdriver. The piston controls the pressure retention of the valve. When you turn on the pressure washer, the piston should move freely. If not, the engine will stall.
Step 3: Clean the piston with kerosene or alcohol to remove dirt. Lubricate it with silicone grease and reinstall it in the unloader valve so it can move freely again. If the piston was already moving freely, you can skip this step.
Step 4: Check the settings on the unloader valve. The amount of pressure depends on the type of cleaning and surface. The setting may be too high, causing the engine to stall when the trigger is pressed. Adjust the settings so the valve opens and cycles the water back to the inlet to prevent too much pressure build-up.
Step 5: The pressure washer may still shut down even with proper unloader valve settings. Check the O-rings, which seal the oil pump. Improper sealing can cause the unloader valve to malfunction. Purchase new O-rings to ensure no oil pump leaks. Reinstall or replace O-rings with grease, thread tape, and grease remover.
Step 6: Double-check the pressure washer before using it. Check:
Engine performance
Water inlet for damage
Air filters if it hasn’t been used in a while
Clean the spark plug with alcohol
Check all these to make sure your pressure washer is in good working order before cleaning patios or decks.
How To Prevent A Pressure Washer From Cutting Off When Pull The Trigger
If you have read the details of the above sections, you will know that the main cause of the problem of the pressure washer shut off when pulling the trigger. So in this section, we will give you some tips about maintaining your pressure washer to limit the above problem that may occur:
Clean the unloader valve regularly. Remove any dirt, debris, and mineral buildup from the valve and springs. This will help ensure parts move freely
Check and replace worn O-rings. Cracked or damaged O-rings can cause leaks that reduce pressure, triggering the cutoff. Replace O-rings as needed
Lubricate moving parts. Spray appropriate lubricant on springs, shafts, and other parts to keep everything working smoothly
Take it to a professional. If the above steps don't resolve the issue, you may need to have a professional service the valve or other internal parts.
Accessories For Replacing in Pressure Washer
Here are the parts we recommend replacing over an extended period of time with your pressure washer as they can get old and damaged. Refer to the list below:
