Pacifichydrostar 1650 pump pulses when pulling the trigger

disposable product, Hardware stores have replacements.

Things to check:
1) is water coming out of the bottom of the pump or is the oil in the crankcase high level and milky yellow. If so your seals are bad.

2) Your check valves might not be seating properly. A couple of fouled check vavles will cause either no pressure or pulsing pressure. A good inlet water strainer keeps foreign matter out of valves. But valves do wear out and get build up that keeps them from working right.

3) Your unloader valve might be worn or fouled. Bad unloader would usually show as low pressure ( but more than hose pressure) or low volume out the trigger nozzle.

Valves are your most likely problem.

dont know the model or if it has a pressure switch inside the box but try and remove your lance and just operate the gun... if it runs ok your last could be blocked

When you feel a pulsing from your pleasure washer you have a bad inlet or outlet check valve. Inspect and clean all check valves

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

I am not 100% certain, but to the best of my knowledge, on this car, the safety circuit monitors only for a spark pulse. It is not connected to the SRS system. If you kill the engine (as often occurs in an accident) and it does not detect the ignition pulse it expects, it shuts off the fuel pump.
I had an '87 once that would not cycle back on when everything was fixed. I had to short between fuses #4 and #6 to 'hot wire' the fuel pump to start the car. Once I had started the car and turned it off normally, I removed my jumper from the fuses and everything worked fine.

Check the wire feed does not become obstructed when the trigger is pulsed. The wire can become tangled on the roll if it is able to get loose. The reel tension must be adjusted as the weight of the roll decreases.

depending on amount of use i have found failures of the piston spring and retainer which are located inside main housing of pump,these cause pulsing and no pressure,you need to remove pump head and face plate to get to them,hope this is of help

you have a restriction in the nozzle end of the lance. clean with paper clip.
if not you have some dirt in the pump head valves which need cleaning

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.