[77newell]

I'm not absolutely sure of this but I seem to recall having one of those black accumulators in an earlier coach and if I recall correctly there was no bladder in it to separate the water and the air. When there was water pressure and you pressed the shrader valve I always got water. The air would slowly dissolve in the water so it needed added air now and then unlike the accumulators with bladders. In no case that I can think of would a failed accumulator cause more than fast cycling when using the pump. If water pressure is low when using the pump there is either a bad pump with internal recycling, a restriction in the piping or valves or you are low on water in the tank (which would be evidenced by air burping out of faucets when turned on)

All I can otherwise suggest is follow the water from a known pressure source all the way to the needed faucet. If pressure is low or nonexistent in all faucets the problem has to be in a location shared by all, usually in that octopus of valves in the water bay which may or may not be original.