Based on the fact that your generator starts when you add fuel to it means that your generator has a fuel supply problem, there could be a couple of causes to the fuel supply problem with your Generator.
The first thing I would do is check for a blocked Fuel Filter on the Generator itself or an in-line fuel filter on the fuel supply line leading from your RV's fuel tank to the generator.
It could also be a loose fuel line connection on the generator or fuel tank or a cracked or leaking fuel line. You need to thoroughly check the fuel line from the generator to the fuel tank. A cracked, loose or leaking line will not allow the fuel pump on your generator to develop suction and pull the fuel into the generator.
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