Burner Switch is in OFF Position – Place burner switch in ON positionDiesel Fuel Level is Too Low – Refill burner fuel tank with #2 diesel, kerosene or other approved fuelTrigger Gun Released – Squeeze trigger gun. Water must be spraying in order for burner to light.Thermostat Set Too Low or Faulty Thermostat – Increase thermostat to desired temperature or replace thermostatBlown Fuse – Many hot water pressure washers have a fuse in the control box. Replace fuse as needed.Gas or Diesel Engine is Running Too Slow – We recommend always running pressure washer engines at full throttle. Move throttle level to full throttle position to correct.Fuel Filter is Clogged – Clean or replace fuel filterSpray Tip Nozzle Not Installed – Most hot water pressure washers will not allow the burner to ignite unless producing high pressure water. Installing a high pressure nozzle and pulling the trigger gun will allow the burner to ignite.Faulty Pressure Switch, Flow Switch or Vacuum Switch – These three different switches all control the burner ignition. A pressure switch must sense high pressure through the system prior to burner ignition; vacuum switches and flow switches must sense water flow, but not necessarily at high pressure. If these switches are not operating properly, they can cause lack of hot water production by the pressure washer, as well as prohibiting the burner from shutting off after the trigger gun is released. Replace switch.