Gas pressure washer won't start

Q: Gas pressure washer won't start

In Canada, a gas pressure washer that won't start after off-season storage is most often suffering from stale fuel gumming up the carburetor — pump gasoline goes bad in a few months and clogs the tiny passages. Before that, run the basic start sequence: fuel valve on, choke set, primer pressed. Then rule out a fouled spark plug, low engine oil (many engines have a low-oil sensor that blocks starting), and a clogged air filter. Never run a gas engine indoors or in a closed garage — the exhaust contains carbon monoxide. If you smell a strong fuel leak, stop and let it clear before doing anything else.

A pressure washer that won't fire up after sitting is one of the most common — and most fixable — small-engine problems. Nine times out of ten it's the fuel or a simple start-up step, not a dead engine.

tuneWhat are you noticing?

Select anything that matches and the checklist below reorders to fit. Not sure? Skip it.

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In Canada, if the washer sat over the off-season with fuel in it, suspect stale gas in the carburetor first — the single most common no-start. Start by draining the old fuel and refilling with fresh gasoline; if it still won't catch, the carburetor likely needs cleaning. Carburetor work is fiddly, and if you're not comfortable with it a small-engine shop can clean or rebuild it quickly.

Ranked from real-world failure data. The order updates as you select what you’re noticing above.

Likely causes, in the order to check them

Showing the typical order

Beginner-friendly Doable, with care Safety-critical Call a pro

handymanHow to fix it

report Fuel, pressure, and fire before you open the carburetorYou're working with gasoline, so do everything outdoors in open air — never in a closed garage — with no flames, sparks, or cigarettes nearby, and keep a way to wipe up spills. Relieve the water pressure at the spray gun and pull the spark-plug boot first so the engine can't start. Gasoline vapour ignites easily; if you smell a strong leak, stop and let it clear before continuing. Carburetor work is fiddly — if it's more than you want to take on, a small-engine shop is a quick, affordable fallback.

Drain the old fuel, refill with fresh gasoline (ideally with fuel stabilizer), and if that doesn't do it, clean the carburetor bowl and jets — or hand the carburetor to a small-engine shop if the varnish is heavy.

Outdoors in open air, with the engine cool and the spark-plug boot removed, drain the stale fuel into an approved fuel container — never down a drain.
Refill with fresh gasoline. A fuel stabilizer helps it keep over the next off-season and prevents the varnish that caused this.
Try starting. If it still won't run, remove the carburetor bowl, clean the varnish out of the bowl and the tiny main jet, and spray carburetor cleaner through the passages. Reassemble and try again.
If the carburetor is heavily gummed or you're not comfortable splitting it apart, a small-engine shop can clean or rebuild it — often cheaper than a wrong parts order.

schedule60 min savings$0–30

Fuel stabilizerAny major brand; add to every can of small-engine gas at fill-up Carburetor rebuild/clean kitMatch the kit to your engine make and model number stamped on the engine shroud

gavel Check your province first AB: homeowner may do this · BC: homeowner may do this · ON: homeowner may do this · PE: homeowner may do this · QC: homeowner may do this
Homeowner maintenance of a gas pressure washer — fuel, carburetor cleaning, and spark-plug service — is routine and permitted in every province and territory.

visibilityHow to check the spark plug

report Relieve the pressure and disable the engine firstBefore you touch the plug, squeeze the spray-gun trigger with the engine off to release trapped water pressure, then pull the spark-plug boot so the engine can't suddenly fire and pull your fingers into the recoil. Work outdoors in open air only — never in a closed garage. If any of this feels beyond you, a small-engine shop will check the plug in minutes.

Relieve the water pressure first: with the engine off, squeeze the spray-gun trigger until no more water comes out, then pull the spark-plug boot off so the engine cannot fire while you work.
Remove the spark plug with a plug socket and read the tip: light tan is healthy; wet with fuel, sooty black, or oily all point to a fouled plug.
Check the gap against the engine's spec with a gap gauge, and look for cracked porcelain or a worn electrode. Clean and re-gap a lightly fouled plug, or fit a fresh one if it's worn or wet.

buildspark-plug socketbuildgap gauge schedule20 min

handymanHow to fix it

report Release the pressure and disable the engineSqueeze the spray-gun trigger to release trapped water pressure and pull the spark-plug boot before you start, so the recoil can't fire the engine while your hands are on it. Work outdoors in open air, never in a closed garage. If the plug is seized or you're unsure of the gap, a small-engine shop will sort it quickly.

Relieve the water pressure, pull the plug boot, remove the plug, and either clean and re-gap it or install a fresh matching plug gapped to the engine's spec.

With the engine off, squeeze the spray-gun trigger to release water pressure, then pull the spark-plug boot so the engine can't fire.
Remove the plug, clean light fouling with a wire brush, and set the gap to the engine's spec with a gap gauge — or fit a new plug of the same part number if it's worn or wet.
Thread the plug in by hand to avoid cross-threading, snug it with the socket, push the boot firmly back on, and try starting outdoors in open air.

schedule20 min savings$6–15

Replacement spark plugMatch the part number on the old plug or the engine manual; gap to the engine's spec

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Why the list is in this order

We don’t sort by likelihood alone. We sort the way a good, honest tradesperson thinks: rule out the free, safe, common causes first. That’s why the cheap checks outrank the expensive repairs — and why anything dangerous gets a hard stop instead of a pep talk. The order exists to save you money, not to sell you anything.