Stalls when triger released

Have you tried servicing the motor. Fresh air filter, new fuel filter and a fresh spark plug? That will help narrow down what the problem could be.

Hi Cliff:
My experience is that the pump pressures prevent the engine from starting, so we hold the trigger while starting.
My brother has cut a wedge of wood that he uses to jam the trigger open to bypass the problem. It can get a bit wild if the wand is not secured when the unit is started..

David, pressure relief valve, sticking, defective.

The wand (lance) is bad. I went crazy with the same problem. Replaced the wand and now it works normal.

the most comon problem with thease is a stuck bypass valve, this is the valve that alowes the water to bypass round the pump when the triger is closed, when they stick all of your pressure runs around the pump and not out of your nozzle,,
its located in the centre of the pump on the top, undo the 2 cap screws pull out valve greese and re fit

These units have pressure valves that automatically turn off the pump once the pressure is high enough. The pressure switches do fail and sometimes stick and act as you've described.

check filter in wand and clean out nozzle hole for starters

Your uplift injector valve in the water pump is sticking. You need to remove this part. Lube the top o-ring only with a water proof grease. Reinstall this part. You will be up and running again.

You need to use needle nose vise grip tool to easily remove the valve. You need to grind down the vise grip tool to fit the opening where the valve is installed.

To prevent this problem from reoccuring use a pump guard additive.

To determine if your problem is due to an easily replaceable part, follow these steps:

1. Connect the water supply hose, the pressure hose, and the wand WITHOUT any nozzle tip.

2. Turn on the water supply, and press the trigger until water is smoothly running out of the nozzle
after any air is all purged out. Release the nozzle trigger.

3. Start the engine, and let it warm up for about 30 seconds.

4. With the engine running smoothly, press the nozzle trigger. The water should flow out of the nozzle (without the tip installed) at a faster rate, while the engine noticeably loads down as it used to do before your "no pressure" problem. If it does not load down, turn it OFF, and disconnect everything, and contact a Karcher repair facility.

5. If the engine does load down, release the trigger, and install one of the nozzle tips (not the black one).

6. Press the trigger, and the engine should load down, and you should have normal pressure from the wand. After you release the trigger and press it again, you will probably again have no pressure, and the engine will not load down. Removing the nozzle tip, pressing & releasing the trigger, and re-installing the tip should give you normal pressure again, but releasing the trigger will cause no pressure until you again remove the tip, press the trigger, and re-install the tip.

This is caused by a bad UNLOADER VALVE, which is located under a black cap with a metal button on it located on the top front of the pump. I don't know if you can purchase the replaceable parts from a Karcher repair shop, but when a neighbor & I took his washer to a repair place, it looked pretty simple to do this repair, and he was charged about $60 to replace a $5 (maybe) part, and it took about 5 minutes.

Hi! robcarroll
Did you purge the air from the pump before starting the motor.
InMrFixIt