Only a small volume of water comes out of the faucet

Check the valves at the water inlet setup, you may have it switched to "fill" or "city water" instead of the pump setting. Sounds like it's just trying to prime itself and can't do it because of the valve position. Don't have one of those RVs so I can't be specific. I'm assuming there is water in the fresh tank? If it was only one faucet I'd say the aerator is plugged but you say it also doesn't come out of another faucet.