After reading the thread about not being about to fill our tanks completely and consistantly I got under the rear of my RV checking the fuel lines to the tank. They looked OK. But upon closer examination I found the grounding wire neatly wrapped around the grounding terminal bracket and the other end of the wire not connected to the frame.
The terminal was broken and never repaired. This is the grounding wire for the fuel filler.
It is properly grounded now. But if in 20k miles since we bought the RV, there had been a spark.....