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:
http://i771.photobucket.com/albums/x...lad/pic3-1.jpg
1 situation:
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/x...lad/pic4-1.jpg) because
it stopper the hole to low pressure or put other.
2 situation:
Your original gun or hose (nozzle) there is a blockage. You have to clean
nozzle and hose.
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 pump...
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!

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