Diagnosis
The pulsing means the pump is trying to prime but can't get a consistent water supply. This model's axial cam pump is self-priming, but it needs a solid feed of water to start with.
How to Fix It
Here's the foolproof sequence. 1) Connect your garden hose to the washer and turn the water on full force at the spigot. Let it run for a minute to fill the hose completely. 2) With the washer OFF and the spray gun trigger locked closed, squeeze the trigger on the gun for two seconds, then release. You'll hear air hiss out—that's good. Do this 2-3 times. 3) Now, plug in the washer, pull the trigger on the gun, and turn the machine on. It should catch and smooth out within 5-10 seconds.
If That Didn't Work
Double-check that you're using the correct spray tip. If you have it on the soap applicator tip (the black one with the bottle attachment), it won't build full pressure. Switch to one of the colored high-pressure tips (white, green, or red).
Heads Up
Always start the pressure washer with the trigger pulled. Starting it with the trigger closed puts an immediate strain on the pump and motor, which can cause that pulsing or even trip the thermal overload.