A part of my foundation has been in need of repair for quite some time. I
now have the opportunity to do this, but after looking at it today, I'm not
sure I can handle the task. I really want to try it, but not sure how to
proceed.

The damage I'm seeing isn't like the web info I keep coming across, so
that's the reason for my uncertainty as to a repair course. I've decided to
take some pictures and will explain each below.

The first damage I describe as a "foundation gap" of around 2-3" deep by
nearly 36" long.
http://img241.imageshack.us/img241/3...ndationgap.jpg
To make matters worse, parts of the gap are quite deep and I can fit at
least half of the yard stick in spots:
http://img35.imageshack.us/img35/138...ongapdepth.jpg
I can easily chisel and break parts of I guess what would be the cinderblock
within the deep depth. Very easy to break and crumble. There is also some
foam filler someone attempted to inject, but I have removed most of that.
Lots of dirt and debris around this area. The big question is how do I
repair this gap? Can I just fill in with cement and what type and how would
I go about cleaning the entire area?

Lastly, there is a crack just beyond the gap:
http://img19.imageshack.us/img19/171...ationcrack.jpg
I assume this could be filled in with hydraulic cement patching that I keep
reading about.

There you have it. I can't find anything on repairing this type of
foundation separation/ decay damage and all I keep running across are cracks
or small to moderate sized holes, so any advice would be greatly
appreciated. Just to note, the separation only occurs at one end of my
house and is about 36" long as I said. The rest of the foundation in other
areas seems intact and not separated, plus there are no cracks. Any idea of
the cause of this would be appreciated also so, if I can repair it, it
doesn't happen again.

Thanks in advance,
Bill Skype