Hallo from Bulgaria. I have the same water pressure pump. The question is old
but naw I saw it.
The problem comes from valve in this modul:
If you are change hose and gun, the nozzle in new gun is with small diametar.
The water pressure pump have more debit from this who may come from nozzle. Then
the pressure push the valve and valve close the holes for pressure of pump. So
the pressure pump works pulses and the pump load. Уou need to remove the moving
part of the valve, but you must keep the bolt
http://i771.photobucket.com/albums/xx351/Tafflad/pic4-1.jpg) because it stopper
the hole to low pressure or put other.
Your original gun or hose (nozzle) there is a blockage. You have to clean nozzle
Do not worry if you remove the valve. In this water pressure pump, valve is in
stupid situation. It can not safe the pump or other components - on the
contrary, it is placed to adjust to a small range by pressure knob at the front
end of the machine. It work good but when all in the machine is original. When
you ruduce the pressure the valve make pulses again but it is so small that you
can not feel. But one thing is certain - when valve work, it difficult the
I am remove the valve many years ago and it has no problem.
Sorry if my english is not vary well, but I am from Bulgaria.
I hope I've helped, if there is still a problem!