Purchased a 16' Scamp that had been stored for many years. In process of verifyiing everything works. Refrigerator is both 120 volt and propane. Works great with electric but having trouble with propane. I purged the gas lines with the stove and know I have gas pressure. BUT...how long do you hold the gas valve in to insure gas to refrigerator burner?? Also any way to verify spark generator is working???