How to Start a Gas Pressure Washer, Step by Step

Before you pull the cord: the short version

Starting a gas pressure washer is a lot like starting a lawn mower, with one extra job: the pump needs water before the engine runs. Most starting problems come from skipping a pre-start check, using old fuel, or leaving air trapped in the pump.

Exact control positions differ by brand and engine, so treat the steps below as the general pattern and check your manual for the specifics. A washer like the IvyBess 4200 PSI model in our data uses a 212cc 4-stroke engine with a pull-start. The Simpson Aluminum Series uses a Honda GX390 engine with low-oil shutdown. Both follow the same basic routine.

Safety first

A gas washer combines a running engine, flammable fuel and a very strong jet of water. A few habits prevent most injuries.

• Run it outdoors only, well away from windows, doors and garages. Engine exhaust contains carbon monoxide, which you cannot see or smell reliably.
• Let the engine cool before you refuel, and wipe up any spills before you start. The muffler and engine get hot enough to burn skin.
• Wear safety glasses or goggles, closed-toe shoes and hearing protection. Debris can fly back at you, and small engines are loud.
• Never point the wand at people, pets or your own feet. A high-pressure jet can cut skin and force water and dirt under it.
• Keep the spray gun's safety lock engaged whenever you are not actively spraying, and brace for a small push when you squeeze the trigger.

Step-by-step: how to start it

Set the washer on level ground so the oil reading is accurate and the unit cannot roll. Then work through the list in order.

• Check the engine oil with the washer level. Low oil is a common reason an engine will not start, especially on engines with a low-oil shutdown feature like the Honda GX390 on the Simpson model.
• Check the fuel. Use fresh gasoline in the grade your manual calls for. Our IvyBess example lists a 3.6L fuel tank, so a fill-up gives a decent working session.
• Connect the garden hose to the water inlet and tighten it by hand. If your washer has an inlet screen, make sure it is clean.
• Attach the high-pressure hose to the pump and to the spray gun, then fit the wand and a nozzle. Quick-connect nozzles should click into place.
• Turn the water on fully at the spigot. Squeeze the trigger and hold it until a steady stream comes out with no sputtering. This pushes trapped air out of the pump and hoses.
• Open the fuel valve if your unit has one, then set the choke. A cold engine usually needs the choke closed. A warm engine usually needs it open.
• Set the throttle as your manual directs, then switch the engine switch to on.
• Pull the starter rope with a firm, smooth stroke. Do not yank it all the way out and let it snap back. Once the engine catches, move the choke back to the run position gradually.
• Let it idle for a short moment, then squeeze the trigger and start cleaning.

Can you start a gas pressure washer without water?

The engine will physically start without water, but you should not do it. Water does two jobs in the pump: it moves through the pump to build pressure, and it carries away the heat made by the moving parts. Without it, the pump heats up quickly and the seals can be damaged. That kind of damage is not always covered as normal wear.

The safe habit is simple. Connect and turn on the water first, purge the air, and only then start the engine. When you finish, shut the engine off before you turn off the water. If the engine is running while you are not spraying for more than a minute or two, shut it down rather than letting the pump circulate hot water, since many pumps heat up when the trigger is released and water is not flowing out.

If it will not start: quick troubleshooting

If none of that helps, check the spark plug and air filter, which are inexpensive and easy to inspect. If you are still stuck, a small engine shop can diagnose carburetor problems.

Fuel habits that make starting easier

Many hard-start problems trace back to fuel that has sat too long. Gasoline can break down over a few months and gum up a small carburetor. If you only use your washer a few times a year, run it low on fuel before storage or follow your manual's guidance on stabilizer.

A clean, correct fuel container also helps, because dirty or leaky cans cause spills and contamination. If you are shopping for one, our best gas can comparison covers the options. Keep fuel in an approved container, away from heat and ignition sources, and never store it in the living space of your home.

Pick the right nozzle and wrap up

Once the machine is running, start with a wide nozzle. Narrow 0 degree and 15 degree tips can gouge wood and strip paint, so begin with a 25 degree or 40 degree nozzle on decks, siding and cars. Use the soap nozzle for detergent, and keep your first pass a bit farther from the surface than you think you need.

If you are still choosing a machine, our best gas pressure washer page compares models side by side by PSI, GPM, engine, hose length and weight. Weights in our data run from 50 to 133 lb, so think about how often you will move it before you buy.

Frequently asked questions

Why does my pressure washer start and then stall when I squeeze the trigger?

Common causes are air in the pump, a clogged inlet screen, low water flow from the spigot, or an engine that has not warmed up. Make sure the water is fully on, purge the pump, and let the engine warm up before spraying.

Should the choke be on or off when starting?

On most small engines, a cold start needs the choke closed, and a warm restart needs it open or only partly closed. Move it to the run position as the engine warms up. Check your manual, because some engines use an automatic choke.

How long should I run the water before starting the engine?

Hold the trigger until the stream is steady and has no air bursts. For most machines this takes only a short time, but a longer hose may take a little longer.

Can I use the washer right away after starting it?

Yes, once the engine is running smoothly and the choke is off. Give it a short moment to settle, then start with a wide nozzle.