Smoke blows from the pressure washer's exhaust if the engine is overfilled with oil. Place the pressure washer on a level surface and check the oil level using the dipstick. If the engine is overfilled with oil, drain oil to within the proper range.
An improper fuel/air mix can also cause the engine to smoke. Check the engine choke for the proper setting. A choke that won't open causes excessive smoke. Check your carburetor system and rebuild or replace the carburetor if necessary.
Tune up the pressure washer engine to help eliminate exhaust smoke. A tune-up includes changing the oil, checking the ignition system and adjusting the throttle and choke controls.