Surging, stalling, weak pressure, leaks, or soap that won't draw — a gas pressure washer's problems feel scattered, but most trace back to a handful of parts. Find your symptom below and work it cheapest fix first.
Each guide below takes one specific complaint and walks it in cheapest-first order — the free checks before the paid parts, and the pump last, not first. If you're not sure where to begin, start with the unloader valve: it's the single part behind more pressure washer symptoms than any other, and understanding it makes the rest of the map click into place.
The one part behind surging, stalling, and weak pressure. Learn what it does and how to test it before you ever buy a pump — then the symptom guides make sense.
Read the guide → Symptom · BypassRevs up and down or pulses when you release the trigger. A bypass problem — diagnosed from trapped air through the unloader.
Read the guide → Symptom · BypassRuns fine spraying, dies the instant you let off. The pump isn't entering bypass — from throttle setting to the unloader.
Read the guide → Symptom · PressurePressure throbs high and low with the trigger held. Usually water supply, nozzle, or check valves — the unloader comes last.
Read the guide → Symptom · DetergentSprays water fine but no detergent. The one symptom that lives downstream at the injector — start with the nozzle and pressure setting.
Read the guide → Symptom · LeakWater pooling underneath. Diagnose it by where it comes from — fittings and the thermal release valve before pump seals.
Read the guide → Symptom · StartingRan fine when you stored it, dead after a season in the shed. Almost always stale fuel and a gummed carburetor — diagnosed fuel-first.
Read the guide →Work any of these symptoms far enough and you'll keep arriving at the same part. The unloader valve controls where water goes when you release the trigger, and when it sticks, wears, or falls out of adjustment, it shows up as surging, stalling, weak pressure, or a pump-head leak. If you only read one guide here, make it the unloader valve explainer — it's the key to the rest.
Looking at the tool itself rather than a fault? See leaf blower vs pressure washer for gutters, or browse all our editorial guides.