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The order is water, air, then motor — and on a gas machine you must hold the spray gun trigger open while you pull. Connect the garden hose, turn the tap fully on, remove the nozzle and squeeze the trigger until water runs steadily for ten to fifteen seconds. That purges air from the pump. Then start the motor. Skip the water step and you run the pump dry, which scores the seals; skip the trigger step on a gas unit and the recoil cord will feel welded in place, because you are pulling against a hydraulic lock.
Below is the full sequence for both machine types, then the six reasons a pressure washer refuses to start, in the order they actually occur.
Starting an Electric Pressure Washer
- Connect the garden hose and turn the water fully on. Use a 5/8-inch hose, uncoiled, as short as practical. A coiled 1/2-inch hose can fail to supply a 1.76 GPM pump.
- Check the inlet screen. Pull the small filter from the water inlet and rinse it. A blocked screen starves the pump and causes the pulsing owners usually blame on the house water pressure.
- Purge the air. With the machine off and no nozzle fitted, squeeze the trigger until the stream runs steady and quiet.
- Plug into a GFCI-protected outlet and press the RESET button on the module built into the power cord. It should click firmly. If it trips again immediately, stop — that is a fault, not a nuisance.
- Hold the trigger open and switch the machine on. Starting with the trigger held means the motor spins up against no load.
- Fit your nozzle. Release the trigger, engage the safety catch, push the quick-connect on until it clicks, then tug it to confirm it is locked. An unlocked tip becomes a projectile.
Shut down in reverse: release the trigger, switch off, turn the water off, then squeeze the trigger once more to bleed the residual pressure before you disconnect anything.
Starting a Gas Pressure Washer
- Check the engine oil. Most residential gas washers have no low-oil protection on the pump and only a basic sensor on the engine. Ten seconds now saves a rebuild.
- Connect the water and purge the air, exactly as above. This matters more on gas machines, because the higher-output pumps are less forgiving of running dry.
- Open the fuel valve. On most engines this is a lever under the tank, turned to ON or the vertical position.
- Close the choke for a cold engine — the lever moves toward the CHOKE or closed symbol. A warm engine usually needs no choke at all, and choking a warm engine floods it.
- Set the throttle to fast if the machine has a separate throttle lever. Many modern residential units are fixed-throttle and skip this.
- Squeeze and hold the spray gun trigger. This is the step everyone misses. It relieves the pressure trapped in the pump so the engine can actually turn over.
- Pull the recoil handle. Draw it out slowly until you feel resistance — the compression stroke — then pull briskly and smoothly through. Never let the cord snap back; guide it in.
- Open the choke gradually over the first 20 to 30 seconds as the engine warms and smooths out.
Shut down in the reverse order: release the trigger, move the engine switch to OFF, close the fuel valve, turn the water off, then squeeze the trigger to bleed the line.
Why It Won't Start: Six Causes in Order of Likelihood
| Symptom | Most likely cause | Fix |
|---|---|---|
| Recoil cord will barely move | Trapped pump pressure | Hold the trigger open while pulling |
| Fires, runs 3–5 seconds, dies | Blocked carburettor jet from stale fuel | Drain the bowl, refill with fresh fuel, clean the jet |
| Turns over, never fires | No fuel reaching the cylinder, or fuel valve closed | Open the valve, check for fresh fuel, check the spark plug |
| Electric hums, does not spin | Starting under pressure, or a failed capacitor | Bleed the line and start with the trigger held; if it persists, service |
| Electric completely dead | Tripped GFCI on the cord, or a tripped breaker | Press RESET on the cord module; check the circuit |
| Starts, but no pressure at the wand | Air still in the pump, or a blocked inlet screen | Purge with the nozzle off; rinse the inlet filter |
Stale Fuel: The Reason Most Gas Machines Fail in Spring
Small engines are far more sensitive to fuel age than cars, and pressure washers sit unused longer than almost any other outdoor tool. Pump gasoline containing up to 10% ethanol begins to oxidise within about 30 days, and ethanol is hygroscopic — it draws moisture out of the air. Given a season in a vented tank, the fuel can separate, and the residue left behind forms a varnish that blocks the carburettor's main jet.
The engineering detail that explains the symptom: that jet is a calibrated orifice often smaller than a sewing pin. A partial blockage lets enough fuel through to fire the engine on the prime in the bowl, then starves it — which is exactly the "runs for four seconds and dies" pattern. No amount of pulling fixes it, and neither does fresh fuel poured on top; the bowl has to come off.
Preventing it takes two minutes at the end of the season. Either run the tank dry with the fuel valve closed until the engine stops on its own, or fill the tank and add a fuel stabiliser at the dose on the bottle, then run the engine for five minutes so treated fuel reaches the carburettor. The second method is better for the fuel system's rubber components.
The Other Winter Failure: A Seized Pump
If the engine starts easily but the machine makes an unhealthy noise, or the pull is still heavy with the trigger held, suspect the pump rather than the engine. Water left in a pump through a hard freeze expands and can crack the head or distort the valves, and pumps left wet without freezing can corrode internally over a long storage. This is the real story behind most "it lost pressure over the winter" complaints.
The prevention is a bottle of pump antifreeze and about ninety seconds: disconnect the water, run the machine briefly to expel what is inside, then feed pump saver into the inlet until it comes out of the outlet. It also lubricates the seals, which is worth doing even in a climate that never freezes.
Before You Pull the Trigger
Two safety points belong in any starting routine. First, gas pressure washers must never be run indoors, in a garage, or in any partly enclosed space — including with the door open. Small engines produce carbon monoxide in quantities that are lethal in enclosed air, and it is odourless. Second, the machine becomes dangerous the moment it is running: a high-pressure stream can penetrate skin and inject water and debris into the tissue underneath through a puncture that looks trivial. The clinical literature on high-pressure injection injuries treats them as surgical emergencies for exactly that reason. Engage the trigger safety catch whenever you are not spraying, never point the wand at anyone, and treat the red 0° nozzle as one you essentially never fit.
If your machine is electric, confirm the GFCI module on the cord tests and resets properly before every use. The Consumer Product Safety Commission recalled a long list of imported electric pressure washers through 2026 for shipping without one at all.
Where to Go Next
Once it is running, how to use a pressure washer covers nozzle choice, detergent dwell time and the technique that prevents surface damage. If it starts but drips, pressure washer leaking water diagnoses it by where the leak appears. If the pump is genuinely dead, best pressure washer pump explains how to measure the shaft before you order a replacement — and whether replacing it is worth doing at all. Buying instead? See the best pressure washers and which brands hold up. Everything sits under the leaf blowers and yard cleanup hub.
We never buy or physically run the machines we write about — our guidance comes from aggregated owner reviews, manufacturer documentation and published research. Method: how we rank.