I own a waterproofing company in Ann Arbor Michigan. We have injected thousands of leaking cracks with sucess. We use high pressure injected poly-urethane. The PU is injected at up to 3000 psi from the inside. This forces the grouting material through the crack and into the soil where it gels in the dirt, helping stabilize the void left in the soil from erosion.
We use this method on non-moving cracks or typical dry shrinkage cracks. Epoxy injection is different.
Epoxy bonds the two halfs of the wall back togeather for a structural repair. It is only medium effictive in stopping water. We use epoxy only when a crack needs structural repair (we also have other methods such as carbon kevlar stiching).
The most common repair is low pressure injection. This only works in a very wide crack. If you see a plastic injection port, low pressure injection was used. Our ports are steel or brass. Each injection port has to be drilled into the crack or intersecting it. On the outside of the crack paste is sometimes applied to help develop greater pressure, forcing the PU deeper into the crack and keep the PU from escaping.
You can see photos of a crack repair at our web site www.basementfix.com