Why won't my pressure washer start?

Check carburetor & air filter. Clean off all dirt and clean air filter. check age of gas. Cannot be more than 30 days old. Make sure to use fresh gas w/synthetic 2-cycle oil @ 40:1 ratio (1 gal.) Gas to 3.2 oz. Oil). Do not use old or stale oil/gas mixture. Before putting in fresh fuel, press the primer several times. A small amount of gas might show up in the fuel tank. Remove fuel. With carburetor cleaner, spray carburetor. Put in small amount of fresh fuel. Just enough to cover the fuel filter. Then press primer with fuel cap off, and watch to see if fuel is flowing smoothly. If not or if plastic primer bubble does not come back to original shape after pressing, then you have to take carburetor apart and clean or get new carburetor.

what engine make and model???

did you pull the spark plug out and clean it ? if you did , did you also put the starter cord and turn the motor over without the plug installed to get rid of the 2-cycle oil out of the cylinder ? if not do so.

Ensure that the fuel line is not blocked. Disconnect the small rubber hose from the carburetor. Open the fuel on/off lever and see if fuel runs out of the hose, it should. If not, you probably have a blockage in the hoses, the on/off valve is blocked with debris or sludge, or the small bronze filet inside your fuel tank is blocked also. Take fuel tank off to check for blockage of the fitting. Simple process and you only need a 10mm socket.

Check age of gas. Cannot be more than 30 days old. Make sure to use fresh gas w/synthetic 2-cycle oil @ 40:1 ratio (1 gal.) Gas to 3.2 oz. Oil). Do not use old or stale oil/gas mixture. Always use the proper oil/gas mix. If you do not, your engine will suffer rapid, permanent damage. May need to clean or replace carburetor.

Here is the long answer with everything we learned while using a power washer twice a day for years::
This assumes you did not turn power washer over or on its side to drain oil, or dirty oil will flow into carburetor requiring complete carburetor cleaning.

It sounds like could be one of the problems listed below or a combination of those things.
1) The exhaust is partially blocked. Check the screen covering exhaust port for carbon and dirt build-up. High-speed exhaust air must pass freely. We finally broke the exhaust screen out with a screwdriver to get our machine going one day.
2) Gas is not flowing freely to carburetor > under gas tank, find the rubber hose connected to carburetor. Pull off rubber hose and make sure gas flows freely. You can use this hose to drain gas tank of old gas ... and then put in fresh gas.
3) Carburetor is partially gummed up and engine cuts off when gas flow slows down. Buy some gum out, and then don't store power washer with gasoline in the tank. Or put additive in gas when storing machine.
4) The choke is letting in too much gas or not enough gas. Try different adjustments. The choke-lever on our power washer got so bad that we could not set throttle at full open or the machine would die. We still use the machine at 2/3 throttle, and then start it each time using WD-40 as described below.
5) Dirty air filter that won't let engine breath enough air to keep up with combustion. Take off air filter and see if problem persists.
6) The spark coil is going bad?? Change spark plug to see if problem persists. Is spark plug wire pushed all the way onto the spark plug?

Now the nitty gritty: we're gonna start that thing right now
7) Take off air filter. Spray WD-40 directly into carburetor. Yes, we use WD-40 every time to start my power washer, and we use the washer twice a week.
Spray in the WD-40, Pull the engine cord. The engine will fire on WD-40. Guaranteed.
Once it starts, keep spraying WD-40 directly into carburetor to keep engine going.
If engine will not fire and keep going on WD-40, then your spark is suspect.
If your engine fires and runs on WD-40 but dies without it, then your gas supply or carburetor are suspect
8) Carburetor problem >>> try Gum out >>> and then take machine to small engine repair shop
9) Spark ... take out spark plug. Put spark wire back on. Hold spark plug by spark wire. Touch metal threads of spark plug to metal opening where plug came out. Metal to metal. Pull back start cord and look for spark between the metal.
If you have no spark, then spark coil is bad >>> take machine to small engine repair shop

Add a comment if you need more help

Hello
You should siphon out all the old gas you can. Replace with new gas. Check that the spark plug is good and the air filter is clean. Spray some carb cleaner in the carburetor.. Also, you should check the oil level and change the oil if it is black. If it tries to start after you spray the carb cleaner in but won't keep going then you know the carburetor needs a good cleaning

You can try spraying some carburetor cleaner into the carb. If it starts for a minute, your carburetor need cleaning. When you added new gas did you remove the old gas first? Is the air filter clean?

Empty the gas tank and, if you dare to try, the carb bowl too. If you don't dare don't worry about it. Refill with fresh gas, start it up and let it run. If it doesn;t run too good trying cleaning or changing the plug.