OK, thanks, that answers my questions on what the f.accumulator does but how do I test it? Does it have a diaphragm? Should air flow freely through it? Does it just sit there and supply pressure because half of it will be full of compressed air? Just trying to understand the mechanics of the system.

__________________
1999 E320 (gave to daughter) 250K
1994 F150 (may be the end of its road) 240K
1989 560 SL (Reassembly after paint job) 160K
1986 560 SL (deceased., gave it's life protecting my wife)
1988 300 TE (departed)
1994 945T (still running strong with an upgraded cam) 349K
1986 242Ti (deceased)
1968 GT500KR (under restoration)