HELP? Repair of cinder block foundation

yeah you need to find out why those cracks are there they are huge I would not just fill them with out finding the cause.

poured would not be all that old either but block could be 80 years or so which is pretty old. By he picture it looks like it has been patched in the past and has moved more which would be concerning to me if it were my house. I would be thinking about jacking up and relaying that corner rather than patching if it were mine.

Wherever you see one crack, there should be another around a corner or somewhere showing one section has dropped. Premix for patching (I like Quikrete vinyl Concrete Patcher sold at Home Depot) A little more expensive, but it holds up and sticks well.
You can mix a little stone with it to fill large gaps. Or chisel block or brick to correct size pieces to fill gaps.
I have a neighbor friend who is a mason by trade. I buy foreclosed homes and do all my own work with his advice; The trick is to use a rectangular trowel as a "shelf" held against the wall (bottom side up - edge tight against wall) and put the mortar on it with a pointed trowel. Then use the pointed trowel to push it into the crack. Horizontal cracks go fast, pushing it in along the length of the "shelf". Vertical goes slower working across the joint. This is the same method as repointing brick (replacing mortar in brick joints) that you can probably find videos of. It's easy once you learn this trick. This prevents the mortar from falling down the outside of wall and losing it. Something like stone should be put inside to prevent loosing too much down the wall. I tuck scrap Styrofoam in wall voids to prevent mortar loss into wall. Wet the crack with water to slow drying for better bond. There is also what looks and smells like Elmer's glue for masonry made as a bonding agent. Paint the contact surface of the crack first and let tack up for the best adhesion. Available at most masonry supply.
When done, just before it's completely dry, wet looking, but won't come out, brush the surface with a paint brush to smooth it out, giving a professional look. If you don't do this, it will look like an amateur did it.
Horse hair was a common insulation, and was mixed in mortar of the first plaster coat (scratch coat) so the fibers help bind it together. You can cut hemp rope in hair length pieces when repairing plaster in historic buildings to help bind it together for strength as well. Same a strengthening your mortar mix making it less likely to fall out. Consistency of mix is key to using a bit thick with a wet surface - not runny on a dry surface. Read up on "slump test" for proper moisture consistency.

greg13 said:

I would bet that the footer under the foundation blocks is broken. If that is a sump hole in the corner you may have had water undermine the footer. I would dig it up from the outside and see what is really going on.

Greg

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I totally agree dig it up and take it from there I doubt patching will do any good really

yeah there are cracks lots of times but those are huge cracks not the norm

And most 100 yr old foundations are not block can the op tell us how old the house is? Mine is 100+ stone foundation and no cracks btw.