Last Updated on September 25, 2026 by Umar Farooq
**A pressure washer won’t start after winter because of a chain the off-season builds in a fixed order — the fuel goes stale first, that fuel leaves varnish in the carburettor second, water left in the pump freezes third, and a scatter of small winter damage arrives across the whole season — and the only one of those you check *before* you pull the cord is the pump.**
Nothing on your machine broke while you were using it. It went into the garage in October working perfectly, sat still for five or six months doing nothing at all, and came out unable to start. That is not a machine that failed. That is a machine that was left somewhere, and the things that happen to a left machine happen in a predictable sequence.
This page is the seasonal entry point, not the repair manual. Each of the four faults below has a page that owns it properly, and I will hand you over rather than rewrite the procedure badly in four hundred words. What this page is for is the *order* — because the order is the part every spring-startup article leaves out, and getting it wrong is how a five-dollar problem becomes a new machine.
Why a Pressure Washer Won’t Start After Winter: Two Orders, Not One
There are two sequences here, and they are not the same sequence. A winter creates these faults in one order. You check them in a different one, and the difference matters enough to state plainly before anything else.
| What the winter did | When it happened | What you notice in spring | Where it gets answered |
| The fuel went stale | Weeks two to eight | Cranks strongly, coughs once, never runs | Next section |
| Varnish set in the carburettor | Months two to five | Runs on choke, dies the moment it opens | Handed off below |
| Water in the pump froze | One cold night, possibly in January | Cord will not move, or the motor hums | Handed off below |
| Small things accumulated | The whole season | A chewed wire, a stiff fuel line, a dead battery | Last section |
Read down that table and the fuel is first, because it is first. Read it as a to-do list, though, and you will start by draining a tank on a machine whose pump may still have ice in it — and then, quite reasonably, you will pull the cord to see whether the fresh fuel worked.
So the working order inverts one row. The pump gets checked first, by hand, before anything applies torque to it. It takes about ninety seconds and it is the only step on this page where being wrong is expensive. Everything else on the list is patient. Ice is not.
Two boundaries while we are here, so you do not spend your morning on the wrong page. If the engine starts and will only keep running with the choke partly closed, it has already proved it has spark, compression and fuel — that is a metering fault in a blocked low-speed circuit, not a winter no-start. And if the engine runs beautifully while no water comes out of the gun, an inlet check valve that stuck over the winter is a priming and water-delivery problem; the engine in that case is not the patient.
Drain the Tank Before You Diagnose Anything
Here is the position this whole article rests on, and it is the opposite of what troubleshooting normally asks of you: do not diagnose the fuel. Replace it, and diagnose what is left.
The reason is arithmetic. Kawasaki Engines publishes the shortest fuel clock I have found from any maker — its own FAQ says “If storing fuel for more than two weeks, use a fuel stabilizer to prevent gasoline breakdown”. Two weeks. A machine put away after the last warm weekend in October and pulled out in April has sat for something like twenty-four. That is not a close call. Investigating it is how people spend a Saturday proving something they could have assumed in ten minutes and moved on from.
Petrol is a blend, not a substance. The light, volatile fractions — the ones that actually make an ignitable vapour in a cold cylinder — leave first, through the same tank vent that keeps the fuel system breathing. What is left behind is heavier, harder to light at cranking speed, and slowly oxidising. That is why the classic spring symptom is an engine that cranks with real enthusiasm, coughs once as if it is about to catch, and then does nothing. There is fuel. It just will not light.
The ethanol makes it a second problem as well as a first. It pulls water vapour in through that vent all winter, and water goes to the lowest point in the system, which on a pressure washer is the carburettor float bowl — the exact reservoir the jets draw from. Kawasaki is also blunt about blends above E10: “E-15, E-85, and other blends can damage your small engine and void your warranty.” If the machine has been running on whatever the cheap pump offered, that is worth knowing before you conclude anything about the carburettor.
What to actually do, in about fifteen minutes:
1. Siphon the tank into an approved container. Not top it up — empty it.
2. Drain the float bowl, at the drain screw if your engine has one or by slackening the bowl nut over a container if it does not. The tank is the obvious reservoir; the bowl is the one that matters.
3. Look at what came out in daylight. Dark and sour-smelling is oxidised fuel. Beads sitting separately from the fuel are water.
4. Refill from a fresh can, not the one that has been standing in the corner of the garage since last summer. That can is not fuel storage. It is the same problem with a handle on it.
5. Try it. Give it ten minutes of running if it catches rough.
One thing not to do: do not pour stabiliser into old fuel and hope. Stabiliser is a preservative, and preservatives work the way a fridge works on milk — excellent beforehand, completely irrelevant afterwards.
What the Stale Fuel Left Behind
Fresh fuel fixes fuel. It does not fix what the old fuel left behind, and that distinction is the whole second cause.
While the light fractions were evaporating out of the float bowl, the heavy end that stayed was oxidising into the sticky amber film that small-engine mechanics call varnish. It is thin, it is patient, and it settles in exactly the passages you cannot see — including the pilot jet, which is the smallest hole on the machine and therefore the first one to close.
There is a free test for this, and it is the most diagnostic thing you can do with one pull of the cord. Start it on full choke, let it settle, then open the choke. If it runs while the choke is closed and dies within a second or two of opening, the choke was doing the fuel metering, because the circuit that is supposed to do it is blocked. Fresh fuel cannot rinse that out — the engine only pulls fuel through the pilot circuit once the choke is open, so the one condition that would flush it is the condition it cannot reach.
That is a strip-and-clean job, and it is a genuinely fixable one, but it belongs to the page that does it properly rather than to a paragraph here. The full sequence — the drain-and-spray shortcut, what to photograph before you loosen anything, the gaskets to buy in advance, and the rule that nothing metal ever goes through a jet — is in pressure washer carburettor cleaning. Go there once the choke test has told you the answer is yes.
Turn the Pump By Hand Before the Cord Ever Moves
This is the one that is out of sequence on purpose, and it is the only instruction on this page I would call a rule rather than advice.
A pump head is a casting with galleries bored through it that are narrower than a pencil lead, and no amount of tipping the machine upside down in October gets the last few ounces of water out of them. Water expands about 9% as it turns to ice. The casting does not expand at all. Whatever that argument produced happened in January, quietly, with nobody watching.
The problem is that a pump which froze and survived and a pump which froze and split look identical from the outside. They stay identical right up until somebody applies torque. On an electric machine, a motor that cannot turn draws locked-rotor current, makes no cooling airflow and starts cooking its own windings and start capacitor. On a gas machine the engine has torque to spare and simply wins, which means the coupler, the pump shaft or the belt loses instead.
So, before the fuel, before anything:
1. Take the power away. Unplug an electric machine; pull the spark plug lead off a gas one and tuck it clear.
2. Turn it over by hand. On most gas machines the pump is bolted to the crankshaft, so a slow pull on the recoil is turning the pump. It should feel like ordinary compression and nothing else. A dead stop means stop pulling.
3. Pull the inlet screen out and look for ice in the mesh or in the quick-connects. Ice in either place settles the question, and it ends the day rather than starting one.
4. Check the pump oil if yours has a sight glass. Milky, on a machine that has done no work since autumn, is not an ambiguous reading.
If any of that comes back wrong, the thawing, the leak test at garden-hose pressure and the honest question of whether a split casting is worth repairing all live in pressure washer frozen pump. It is the article to read while you wait, because waiting is most of the treatment.
A Mouse, a Fuel Line, a Flat Battery and Thick Oil
The fourth cause is not one cause. It is the accumulated small damage a season does to a stationary object in an unheated building, and the reason it goes last is that none of it explains a no-start on its own as reliably as the first three do. It explains plenty of them together.
A nest in the housing. A machine that has not moved since October is, from a mouse’s point of view, a dry enclosed box full of shredded-fibre opportunities. Nests turn up in the recoil housing, packed into the cooling fins under the shroud, and inside the air filter box. The Internet Center for Wildlife Damage Management puts the consequence for anything with wiring plainly: “Mice often damage large electrical appliances by chewing wiring and insulation, resulting in short circuits, fire hazards, and other costly malfunctions.” On a pull-start petrol machine you get blocked cooling and a filter full of bedding. On anything with a cord, a loom or a battery lead, you get the other thing. Take the air filter cover off and look before you do anything else on this list — it costs one clip and thirty seconds.
A fuel line that perished. Rubber that has spent years swollen and soft with fuel in it, then sat through a winter slowly drying out, comes back shrunken and hard. The cracks appear where the line bends over the frame and where the clamp has been squeezing it. Run it end to end with your fingers: a supple line squashes flat and springs back, a perished one barely moves. A line that has gone stiff will usually also weep, and fuel weeping onto a hot exhaust is a different and more urgent article.
A battery that did not simply go flat. On electric-start machines, the battery has been quietly discharging since autumn, and that is a chemical change rather than an empty tank. Power-Sonic describes sulfation as “the formation or build-up of lead sulfate crystals on the surface and in the pores of the active material of the batteries’ lead plates”, occurring when a battery has been in a low state of charge “for weeks or months,” and says that once it is permanent, “restoration of the battery or reversal of the sulfation, is highly unlikely.” Its storage instruction is to hold the battery above 12.4 volts, kept below 75°F — and it notes that for every 10°F above that, the self-discharge rate doubles. A battery in a warm garage is not resting. It is working through its charge faster than one in a cold one. If yours reads low in April, put it on a charger before you write the machine off, and remember most electric-start units still have a recoil for exactly this morning.
Oil that has gone thick and acidic. Used oil is mildly acidic and has spent five months in contact with bearing surfaces. It is also cold and stiff in a spring garage, and your shoulder is what has to turn the crankshaft through it. Change it before the first start rather than after — the whole point of a fresh-oil interval is that the engine runs on it, not that the crankcase has been emptied at some point. Milky or grey oil is a different finding entirely and means the machine does not run today.
FAQ
Why won’t my pressure washer start after sitting all winter?
In the great majority of cases the fuel degraded and then left varnish behind it, in that order. Drain the tank and the carburettor float bowl, refill from a fresh can and try again. Before you pull the cord at all, though, turn the pump over by hand with the power disconnected — a pump that froze and a pump that is fine feel completely different and look completely identical.
Do I need to drain the old gas, or can I just top up the tank?
Drain it. Topping up dilutes stale fuel with fresh fuel and produces slightly-less-stale fuel, which is not a state anything runs well on. It also leaves the float bowl untouched, and the bowl is the lowest point in the system — the place where water and the heaviest residue have been collecting all winter.
Will fuel stabiliser fix fuel that has already gone stale?
No. Stabiliser is a preservative that slows oxidation in fuel that is still good; it does not reverse the process or restore the light fractions that have already evaporated. Add it to fresh fuel at the end of the season, then run the engine for a few minutes so treated fuel actually reaches the bowl.
How do I know whether the problem is the fuel or the carburettor?
Fresh fuel is the test. If the machine runs properly on a clean tank, it was the fuel. If it starts on full choke and dies the instant you open the choke, the pilot circuit is blocked and fresh fuel will not clear it — that is the carburettor, and it needs the bowl off.
Can a frozen pump stop the engine from starting?
Yes, and it is the version of this problem that costs money. On most gas machines the pump is bolted straight to the crankshaft, so a locked pump means a cord that will not move. On an electric machine, a motor that cannot turn draws locked-rotor current and heats its windings. Disconnect the power, turn it over by hand, and if it will not move, stop.
Should I change the oil before the first start of the season?
Yes, if it was not changed before storage. Used oil is acidic and has been sitting against bearing surfaces for months, and cold thick oil also makes the engine measurably harder to crank. If the oil looks milky or grey, that is water in the crankcase and the machine should not be run until it is sorted.
My machine is electric — why won’t it start after winter?
There is no fuel or carburettor to blame, which removes the first two causes entirely and leaves the other two. Check the pump for ice before pressing anything, then look for a tripped GFCI, a chewed cord or lead, and a motor that will not turn. An electric machine that hums and does not spin is being told something by its pump.
How long can a pressure washer safely sit with fuel in it?
Shorter than most people assume. Kawasaki recommends stabilising fuel stored longer than two weeks, and other makers draw the line between fifteen and thirty days. None of them are describing a winter. If a machine is going away for a season, it wants either stabilised fresh fuel run through the whole system or an empty bowl.
Thirty Seconds in October Is the Whole Article
Read the four causes back and notice what none of them are: a worn part, a fatigued component, a failure that came from work. Every one of them is a consequence of a machine standing still in a building. Pressure washers are very rarely killed by the jobs they do. They are killed by the months between the jobs, which is a genuinely strange thing to say about a tool and is nonetheless the most useful sentence on this site.
So the order, one more time. Turn the pump by hand before anything turns it for you. Then drain the tank and the bowl and refill from a fresh can. Then run the choke test, and if it fails, take the bowl off properly. Then go looking for the small damage — the nest in the shroud, the line gone hard, the battery that sat at half charge since autumn.
And when it is running and you are standing there listening to it, put a note in your phone for the third weekend of October. The full routine is in how to winterize a pressure washer and it takes about fifteen minutes, of which roughly thirty seconds — pump saver through the inlet — is the part that prevents the expensive one. Nobody has ever had a worse spring for having done it.
Verified sources: Kawasaki Engines — FAQs · Internet Center for Wildlife Damage Management — House Mouse Damage Identification · Power-Sonic — What Is a Sulfated Battery and How Do You Prevent It
