Norcold won't work on LP for fridge but freezer OK!

Thank You Old-Biscuit,the service manual will help. Thanks Doug for the trouble shooting directions. Since I have a top vent looks like I need to pull fridge out to clean all properly.
GJAC-I do hear a slight roar from the very blue flame. Burner tube is slightly rusted but slots appear clean and put out flame as suggested in service manual. I do hear a pop occasionally. Worked fine last time used at the end of last year.