When shooting pictures with the fast action mode they are either black or blurry. When it's on Automatic they are fine. Have tried to switch lenses and switched both manual focus and auto. Have taken pictures with this setting before and it just recently started doing this. Need all the help I can get!!
We don't really have enough information and can only start guessing as to what's happening (but there are so many reasons this can happen that it would be a lot of guesses.)
What would really help is to have extremely specific information about what settings you are using and some sample images (preferably images that still have the EXIF data attached... EXIF data is information inside the picture file which contains all the technical data and settings such as the camera model, lens model, camera mode, exposure information, metering information, etc. etc.) Most of us have photo-viewers that let us see this information and it can tell us a lot about why you are getting those restuls.
The fact that your images are fine in full 'automatic' mode suggests it's probably not a defect and is likely the result of settings you are using. But we can't be sure without examples.
Normally when you take photos, you would use "One Shot" focus mode. In those mode that camera wont take a shot until it can confirm focus has been achieved on at least one of the AF points. But if the subject is moving... the camera can focus ... but then the subject moves OUT of focus and the camera will NOT update the focus (not in "One Shot" mode).
If you use "AI Servo" focus mode, the camera WILL continuously update focus as your subject moves.... but the catch is that if you completely press the shutter button, the camera puts priority on taking the shot WHEN you press the shutter down (a full press... not the half-press used to focus & meter). So if you press the shutter before the camera finished focusing you'll get a blurry shot.
You can also get blurry shots if the shutter speed was too slow and you were hand-holding the camera. This would be common if you were shooting in dark/dim settings and/or if you were using a very high f-stop value (tiny aperture opening in the lens so it doesn't let much light through).
If you can post some examples with EXIF data or at least post your specific modes & exposure settings for each shot then there are many here who would be happy to help you understand why you are getting those results and how to avoid getting blurry shots.