crack onto vs run after

crack onto

verb
  • To flirt with; to approach and speak to (someone), seeking romance, love, sex, etc. 

run after

verb
  • To make a determined effort to win someone's affections or to have a sexual relationship with them. 

  • To endeavour to find or obtain. 

  • To follow quickly, often in an effort to catch or catch up with (someone or something). 

How often have the words crack onto and run after occurred in a corpus of books? (source: Google Ngram Viewer )