No or inadequate fuel to burner

 Some hot water pressure washers do not have a gauge on the burner fuel tank.  It's obvious but check to see you have fuel in the tank.  if the machine is sitting on a grade the fuel may be missing the pickup.

Check all the connections to and from the tank, making sure they are all secure.

Also check if there is an air vent on the tank and that it is open.  If not, a vacuum will build up in the tank and stop fuel flow.