How to fix no pressure from Karcher k3 water blaster?

[MitchB]

hi, I have a Karcher K3 water blaster and there is no pressure.  I have bled it, both with it detached at the machine, and also with the gun detached.

Still no pressure.

Any ideas??

TIA

[EricL]

Hello @MitchB 

I'm sorry to hear that you are running into issues with your Karcher K3. If there’s absolutely no pressure at all and it’s just flowing like a garden hose or there is no flow at all, the most common causes on a K3 are either water supply issues, an internal air leak, or a pump valve problem. First thing to double-check is the basics even though they sound obvious. Make sure the tap is fully open, the inlet hose isn’t kinked, and the hose is at least a standard 1/2" with decent flow. The K3 is very sensitive to low flow and will refuse to build pressure if it can’t get enough water.

Next likely culprit is the inlet filter. On the K3 it sits inside the water inlet where the hose screws on. If that mesh filter is blocked with grit, scale, or even fine sand, the pump won’t pressurise properly. Pull it out carefully with needle-nose pliers, rinse it thoroughly, and refit it. This alone fixes a huge number of “no pressure” issues.

If the filter is clean, look at the spray lance. Try running the machine with the lance completely removed from the gun. If you suddenly get strong pressure straight out of the gun, the lance or nozzle is blocked or worn. The Vario lance in particular can clog internally or fail so it never restricts flow enough to build pressure. Sometimes twisting it back and forth while running can free it, but often replacement is the real fix.

If none of that changes anything and the motor sounds normal but you still have zero pressure, then it’s likely an internal pump issue. On K3s this is usually a stuck inlet or outlet valve, or a worn wobble plate or seals. This can happen if it’s been run dry even briefly or stored with water left inside that’s gone stale. Unfortunately, once it’s at that point, it’s no longer a simple external fix.

I would suggest checking if your Karcher is still under warranty. If it is, it's important to have proof of purchase either a docket or perhaps a bank statement indicating the date of purchase. You can then bring it back to the store where you purchased it from and claim your warranty.

If it is out of warranty, I suggest bringing it to a certified Karcher repair center for servicing.   

If you need further assistance, please let us know.

Eric