Hi i have lpg 2lt petrol motorehome van i let the lpg go very low and now once i have filled up again it is not running very good on lpg keeps switching back to petrol on low revs this has no injectors its carburator single port there dose not look like there is any isolation for gas at the tank as i was going to remove the solinoid filter complet replace with new think it could be a fillter blocked but this could not be the case could any one please help.