Have you calibrated your monitor and assigned ICC profiles to your documents?
There are a number of variable that can affect colour printing - there are several colour management experts who contribute to this forum who may be able to offer better advice.
When I want pure gray I check use black ink only. The only issue is that the tonal range is really bad. If you want to do good continuous tone b&w, you really need a dedicated B&W printer that uses a variety of gray and black inks.
Chuck, I've not seen the necessity to use a dedicated B&W printer (with special inks).
Epson's inks since Ultrachrome do a great job of printing monochrome images IF the print/media profile is accurate. Even in the world of offset print - some photobooks are an example - a "rich black" is used as it is often better looking.
Viewing lighting can affect print appearance too, of course. Colour management is a process working towards daylight viewing.
I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer:: co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management
Good to know.