I have a strange issue. I have a black/white layer, and when i print it as is, it is black and white - but if i add a black "color overlay" (yes, it is #000000) and use an opacity of 0-60% (or more) I get a color tint when printing, even if it looks completely B/W in PS. So 7% opacity gives me a pale yellow tint on that layer, while the rest of the B/W project is B/W in print.
I have tried to copy the layer out to a new file, apply the color overlay, flatten image, and move it back to the main project, but it still get this tint.. I use "photoshop manages colors" when printing as well.
Since i have a color element elsewhere in the project, i cannot force the print to be completely B/W.
I've found this article Printing greyscale images and removing unwanted colour tints very detailed and helpful discussing the same issue you've mentioned.
Could you please take a look and let us know if that helps?
A few things to check :
1. You say the layer looks completely black & White in Photoshop. Can you check that it is actually B&W in the info panel using the eyedropper tool set to sample all layers.
2. When using Photoshop manages colours have you picked the correct profile for your printer, ink and paper combination. I produce my own printer profiles and greyscale tracking is just one of the aims of a good profile.
3. Have you turned off all colour adjustments in the printer.
4. If you replace the overlay with a levels adjustment layer to darken the print slightly - do you see the same?