LP water heater - flame up inside of control box?

1990 Atwood water heater. The electronic igniter continues to spark after it begins burning. The flame travels back through burner to the nozzle, and flames up inside the entire control panel through the air regulator slip joint. I have a yellow flame and understand that it needs to be blue to eliminate carbon monoxide. Is there a part or parts that need replacing or do I need a whole new unit?|||you need to have that checked by a pro NOW before you start a fire or an explosion. SHUT IT DOWN.