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Karcher Pressure Washer: Pump & Water Troubleshooting With Fixes

Karcher pressure washers are pretty reliable and offer an excellent solution for cleaning various surfaces. Despite the utility, even some of the best pressure washers can develop problems that need to be identified before they can be fixed. The pump and the water delivery system are critical aspects that must be heeded for the smooth working of a pressure washer.

If a Karcher pressure washer leaks water, check the connections at the pump, high-pressure hose, and spray gun. Ensure that these connections are tight and that the seals and O-rings are fully intact. If the water pressure isn’t ideal, check the nozzles for any blockages and adjust the unloader valve to an optimum setting. If your pump gives off noise or leaks oil, make sure its seals aren’t worn out, and the pump is being lubricated timely.

In this blog post, I will show you how to troubleshoot issues related to the pump and water delivery system for Karcher pressure washers and perform their fixes by yourself.

Karcher Pressure Washer is Leaking Water

Your Karcher pressure washer may leak water from one of the connections. To troubleshoot the water leak, you need to check its connections at the pump and spray gun separately.

Usually, there are three connections from where a leak is likely to occur. The first location is the pump itself. The second location consists of the hose connections to the pump inlet and outlet. And finally, we have the spray gun connection to the high-pressure hose from where water could leak.

● Karcher Pressure Washer: Water Leaking from the Pump

If your Karcher pressure washer leaks directly from the pump, the fault lies in the piston seals that have worn out and need replacement.

Most pressure washer pumps use a positive displacement piston mechanism which pressurizes the water by pushing it across the tubing. The pistons have a seal that prevents water leakage from the pump. These seals tend to wear out after some time, which could result in a leakage. To check this, you may need to remove the pump’s housing and inspect the piston seals for wear and tear.

● Karcher Pressure Washer: Water Leaking from the Hose Connection

If your Karcher pressure washer leaks from the hose connections, the couplings at these connections have worn out and need to be replaced.

A coupling connects the hose to the pump’s low-pressure inlet at the pump. There’s a seal within this coupling that prevents a leak. If leakage occurs at this point, the coupling and its seal are damaged. Similarly, the outlet seal needs to be replaced if a leak occurs at the pump’s outlet connection to the high-pressure hose.

● Karcher Pressure Washer: Water Leaking from the Spray Gun

If your Karcher pressure washer leaks from the spray gun, check the hose-gun connection and press/screw it firmly. Check if the O-ring at the hose outlet is intact.

In most pressure washers, the high-pressure hose connects to the spray gun by a press fit. You should check if the fit is working correctly. If there are screws on it, make sure they are tight enough. If it still leaks, please check the O-ring at the hose and see if it lies there. A missing O-ring may have been causing this leakage.

You can buy all sorts of seals, gaskets, and O-rings for your pressure washer from multiple locations online or from your local dealer.

Karcher Pressure Washer: Water Pressure Problems

If you have trouble with the water pressure of your Karcher pressure washer, check out the troubleshooting guide below.

1. Karcher Pressure Washer: Low Pressure

To troubleshoot low water pressure, ensure adequate water supply and the inlet hose isn’t clogged with debris. Also, check if the nozzle is working correctly.

The water supply at the inlet must be sufficient for the pump to build the correct pressure. Make sure there are no kinks in the inlet hose. Also, most inlet hoses have a debris filter at the pump connection. Check that filter and dislodge any debris stuck in it. If the problem remains after this, ensure that you are using the correct nozzle and it isn’t plugged with any dirt.

2. Karcher Pressure Washer: No Pressure

If your Karcher pressure washer shows a loss of pressure, start by troubleshooting the water supply, the hose, and the nozzle. If that doesn’t help, check the unloader valve and the pump that could be malfunctioning.

While a loss of pressure may have been caused due to debris stuck or an inadequate water supply, in this case, the pump and the unloader valve can be at fault. Gradually adjust the unloader valve by keeping the pump on and the trigger pressed to see if it improves the pressure. If it doesn’t, try replacing the valve. You may also need to inspect your pump’s plungers and O-rings for any damage.

Over time, air bubbles due to cavitation can damage certain pump parts, exhibiting a loss of pressure. Most pumps sell as single units, so you need to take care of that before doing any replacement.

3. Karcher Pressure Washer: Surging Pressure

If your water pressure spikes, ensure your nozzle isn’t worn out. Also, it would help if you loosened the unloader valve to allow more water into the bypass and less into the spray gun.

The unloader valve of your pressure washer bypasses the high-pressure flow either to the pump inlet or the water tank. If your unloader is too tightly adjusted, it hardly bypasses any flow, so the pressure at the gun outlet is too high. Loosening the valve would allow bypass to occur and prevent pressure surges. If this doesn’t fix the issue, check your nozzle for signs of wear and replace it if it’s worn out.

4. Karcher Pressure Washer: Drops Pressure after a Few Seconds

If your water pressure drops after a few seconds, it may be due to a blockage in the nozzle or leaks in your hoses. An incorrectly adjusted unloader valve could also result in this problem.

Conversely to the above case of surging, if the unloader is too loosely set, it can cause a pressure drop at the gun. If the setting is too loose, even a small water pressure would be enough to overcome the spring tension and actuate the bypass. Hence, pressure at the gun exit reduces. Apart from this, inspecting your hose for any holes/leaks would be best. You should also check if your nozzle isn’t stuck with any debris.

5. Karcher Pressure Washer: Strange Noises from Pump

If a strange noise comes from your pump, it may be due to a faulty bearing or damaged connecting rods. Your pump may also give off noise if it isn’t lubricated properly.

Some more expensive models have a pressure washer pump with replaceable oil. More basic pressure washers use a wobble or axial piston pump where oil is added during manufacturing and then permanently sealed. For other models, you must check the oil regularly and change the oil when needed.

Depending on the model, your pressure washer pump needs to be lubricated every three months. Lack of lubrication causes sliding contacts between metal parts and produces noise. In that case, you can try to open your pump and check its bearings. A bearing replacement will probably eliminate the noise if lubricating the pump doesn’t solve the problem.

If you have a permanently sealed pressure washer pump with strange noises, you need to replace the whole pump.

6. Karcher Pressure Washer: Excessive Noise

If your pressure washer makes excessive noise, it can be due to damage to the pump’s internal components, mixing of air in the pump, a broken pump casing, or engine knocking due to bad fuel in the case of a gas model.

When the air gets trapped in a pump, it causes the plungers to produce a large grinding noise that can also cause damage to the seals and connecting rods. If the pump’s casing gets broken, it might result in vibrations that can cause additional noise.

Check the engine’s fuel quality if you have a Karcher gas pressure washer. I recommend always using ethanol-free, unleaded gasoline with a minimum octane number of 87 to reduce engine knocking.

7. Karcher Pressure Washer: Oil Leaking from the Pump

A pump that leaks oil most certainly has a damaged seal or a worn-out O-ring. If your pressure washer has a pump that is not permanently sealed, replace all the seals.

If you have a pump with replaceable oil and your pump warranty has expired, you should consider disassembling it. To replace the oil seals, I recommend buying an oil seal kit containing all sizes of seals and rings. While putting it back, ensure all bolts/fittings are tight enough. To prevent oil leaks in the future, avoid exposure to extreme conditions as it can damage rubber components quite easily.

If you have a pressure washer with a permanently sealed pump, there is no other option than to replace the whole pump.

8. Karcher Pressure Washer: Water in Oil

If water enters the pump oil, it is due to a faulty oil seal in the pump. If this is the case, replace the seal if the pump is not permanently sealed.

Water entering the pump oil makes it look milky. This can be a direct consequence of a faulty oil seal. Replacing the seal requires an entire pump disassembly, including removing the housing, valves, seals, and rings.

I recommend doing this only when the pump has run out of warranty. Under warranty, this should be repaired by the pump manufacturer. This only applies to pressure washers with a pump where you can replace the oil. Most budget pressure washers have a permanently sealed pump, this means that if the pump is damaged or broken, you can only replace it entirely.

9. Karcher Pressure Washer: Soap Not Dispensing from Reservoir

If your pressure washer is not siphoning soap from the reservoir, check if you’re using the right-sized nozzle or not. Also, you must inspect the soap injector kit and replace damaged or worn-out parts where needed.

For the soap injection function, the owner’s manual recommends a specific type of nozzle that provides suitable suction pressure for the detergent. Check that nozzle type and make sure you use that. If that doesn’t fix the issue, check your soap injection kit and ensure there aren’t any blockages in the nozzle. You can buy a chemical injector repair kit to find all the spare parts you need.

Troubleshooting table for a Karcher Pressure Washer

Problem
Cause
Solution
Pressure washer not producing high pressure
Hose with small diameter
Replace your hose with a 1″ (25mm) or 5/8″ (16mm) hose
Restricted water supply to the washer
Check for the kinks and leaks in the hose
Inadequate water supply
Ensure the water source is unobstructed and fully turned on
Clogged intake filter
Remove the filter and rinse it with warm water
Air in the pump
Ensure that the hose and fittings are airtight. Shut off the washer and squeeze the trigger until water flows steadily from the spray tip
Suction tube or detergent bottle not connected properly
Install the suction tube and detergent bottle correctly
Detergent too thick
Dilute the thick detergent by adding water
Obstructed spray tip
Remove the debris with a needle
No pressure tip on the wand
Install a suitable pressure tip at the end of the wand
If your model has a belt, it can be loose.
Tighten or replace the belt.
Problem
Cause
Solution
Pulsing pressure washer (output pressure varies high and low)
Inadequate water supply
Ensure that the water source is fully on and check the hose for kinks and blockage
Obstructed spray tip
Remove the debris with a needle
Pump sucking air
Ensure that the hose and fittings are airtight. Shut off the washer and squeeze the trigger until water flows steadily from the spray tip
Clogged intake filter
Remove the filter and rinse it with warm water
Calcified hose, tip, or trigger
Clean the hose, pressure tip, or trigger with vinegar or a cleaner designed for this purpose
Problem
Cause
Solution
Noisy Pump
Air in the pump
Ensure that the hose and fittings are airtight. Shut off the washer and squeeze the trigger until water flows steadily from the spray tip
Clogged inlet filter
Remove the filter and rinse it with warm water
Pump leaking water
Damaged or worn water seals
Replace the seals with new ones or call a professional
Loose fittings
Ensure that all the fitting are tight
Erratic water pressure, changing up and down
Unloader valve
Check and clean the unloader valve. If in bad shape, replace it
No output pressure. Or motor stops when using the trigger (electric models)
Unloader valve
Check and clean the unloader valve. If in bad shape, replace it

● Troubleshoot Karcher Electric Pressure Washer Motor issues:

Problem
Cause
Solution
Motor won’t start
The power switch is in the “OFF” or “0”  state
Turn the power switch “ON” or “1”
Cord not plugged
Plugin the power cord
Damaged, too long, or improper extension cord
Replace the existing cord with a 25′ (7.6m) 14 AWG cord or a 50′ (15m) 12 AWG cord
Inadequate power from the electrical outlet
Plug the cord in a different outlet
The pressure washer circuit breaker tripped
Wait for the washer to cool down and restart it
Motor buzzes but fails to run
Loss in voltage due to the extension cord
Plug the unit directly into the outlet without an extension cord. If the problem isn’t solved, replace the extension cord
Low supply voltage
Ensure that only the pressure washer runs on that circuit at the time of use
Residual pressure in the system
Shut off the washer and squeeze the trigger to release pressure
Residual friction among the internal components
Cut the water supply and turn the machine ON for 2 to 3 seconds. Try it a couple of times or until the motor starts. Don’t let the machine run dry for more than 3 seconds.
Unit not used for long periods
Call a professional
Motor not working
Faulty Timer
Disconnect the leads from the timer. If your pressure washer doesn’t turn off after the time out, it means that the timer is faulty and you need to replace it.

● Troubleshoot Karcher Gas Pressure Washer engine problems:

Problem
Cause
Solution
Leaks in the spray wand, spray tip or extension
Damaged or broken O-rings or plastic insert
Replace the worn O-rings or call a professional
Pressure washer pump dripping oil
Worn or damaged oil seals
Inspect the oil seals and replace if worn
No water from the washer outlet
The water supply is off
Turn the water supply ON
Kink in the hose, or faucet not fully open
Remove any kinks and debris from the hose or water lines. Check and fully open the faucet.
Problem
Cause
Solution
Motor won’t start
Check the battery
Check if the battery is charged correctly. Charge or replace when in bad condition. Examine the battery terminals for a proper connection. Clean if needed.
Check the fuel filter
Clean the fuel filter if dirty. In that case, check the gas tank, as this is the most likely culprit.
Check the gas supply
Check the fuel level and add if needed. Ensure that the gas can flow to the carburetor. Remove any blockage.
Check the Air-filter
Clean the air filter. Replace when it is in bad condition, or it is a paper air filter.
Check the carburetor
Remove and clean the carburetor with some carb cleaner. It is also possible to clean it without removing it.
Fuel gap blocked
Check that the hole in the fuel cap is open. Clean if needed.
Engine is stalling, or starts and stops
Check the carburetor
Remove and clean the carburetor with some carb cleaner. It is also possible to clean it without removing it.
Air filter
Clean the air filter. Replace when it is in bad condition, or it is a paper air filter.
Check for bad gas
Suppose you have old gas, more than a few months old. It can turn bad. Drain and replace the gas. Next time add a fuel stabilizer.
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