My karcher seems to pulse when on, could this be due to the low water pressure from the hose?

could be unloader valve or leaking valves or worn packing.

https://www.ppe-pressure-washer-parts.com/files/1961581/uploaded/k3.91m.pdf

Isn't there a bleed off valve on the unit. Typically they get stuck and pulsing is the result.

sounds like your unit has a bypass problem either needs adjustment or replaced

i fixed mine works good easy too watch my video step by step i put it on youtube

http://www.youtube.com/watch?v=8XDPDhg_acQ&list=UUiF9Qw4CmLuBqWFGanj1KIA&index=14&feature=plcp

pulsations indicates an pressure controller suffering from a partially blocked jet at the wand end
blocks up p pressure drops off , unblocks starts pressure to repeat the cycle

Could be the input water pressure is not sufficient. There is a pressure valve inside the machine that will cut off the motor if input pressure is too low or non existent.

Try a different source for the water input.

This may not be a motor problem. It sounds like your pump is not working properly and the motor is just following the pump. First thing to do is check for leaks in the pump, wand hose, gun etc. It may also be a blown water seal inside the pump.

Dear Osville,
It is not clear what type of lance or nozzel you have. You said that the machine works fine with the circulating water jet(the turbo). So it seems the machine is fine. I do sometimes service variable nozzels and variable lances. But the best solution is to replace nozzels and variable nozzles and lances with new ones. Regarding the fan spray setting it could have no pressure because it might be in the chemical setting. The chemical setting lets out a fan shape flow of water, but with less pressure. The chemical system only works on low pressure in domestic washers, that is why it needs a low pressure flat spray. The pencil jet has 2 jets comming out because if it is a lance or nozzel with ball bearings, these ball bearings must have stuck in a wrong position. Also 2 jets can come out, due to a damaged nozzel hole.
Altogether, the best advice is to buy a new nozzel or lance...which ever your machine uses. All Karcher machines have their own specific nozzels, lances and high pressure hoses. You cannot change these from one model to another.
Regards,
Fulltech.

what you need to do is, take the screw fitting which goes to the water tank off, then the one that goes from the water tank to the pump head .
then put the one that was in the first place going to the water tank on to the pump and force feed with water.
see if you can see water leaking from any where seals hose.
try running the machine to check the pressure.
if water leaking from pump head you need seals.

Hi the pump surges when there is a leak on it find the leak that should sort your prob.
Hope this helps. Sean