Water heater won't stay litby Sarah Hale
Start with blowing compressed air through the burner tube and combustion chamber to make sure they are clear of debris and the electrodes are clean. Check all the wire connections to make sure they are clean and tight.
The easiest way to determine if it's an Atwood or Suburban is the location of the circuit board. Though there are some exceptions, the Atwood board is usually accessible from the outside of the RV, the Suburban from the inside.
Burner cleaning is about the same for either. If you have an adjustable air shutter loosen the screw shutter (if it's properly adjusted mark the location so you can put it back in the same place). Remove the screws holding the other end of the burner tube - their exact location depends on the brand and model. You may have to remove the electrode assembly separately. Clean out the burner tube and combustion chamber. Carefully remove and clean the orifice - make sure you don't lose any of the little parts some of them have. Put it all back together, making sure the burner tube is centered on the gas line, the other end is centered in the burner tube, and the electrodes are in line with the end of the burner tube. The gap from the ignitor to the probe should be 3/16" and the flame should envelope about the last 1/2" of the flame detector. Adjust the air shutter so that the flame is blue with only small flecks of yellow, and it isn't too loud.
If you have continued problems, the LP pressure is something else that should be checked. If you are getting the spark but it isn't igniting and everything is clean, it's either the LP pressure or a faulty gas valve. Best way to check either is with a manometer but most folks don't have one, so cleaning is a good way to start.