Injecting a "dirty crack" or previously repaired crack can be tricky.
When a crack is previously repaired it usually rips open is small sections, therefore getting an injection to properly fill crack while traveling port to port is not known. Chasing the crack will help, but still may not fully travel into crack itself.
Intersecting crack also is an option. Still you have the unknown of inside the wall. You may also drill to outside and inject a barrier on exterior of wall-or excavate-or may other methods.
Try chasing crack first and inject slowly trying to allow material to locate voids before traveling up to next port.
You state you already purchased kit. You will find some informational videos on Emecole's Website:
http://www.basementandcrawlspaceprod...tic4/index.asp