how the heck do you get the caps on the ends of the injectors without cracking them. i got two on okay but the other four each cracked. the only method i used was to put a 10mm deepwell over it and give a little push. i took more than a little push to get it past the second notch and four of the times they cracked. if someone has a strategy i would love to hear because i dont want to pay $ 3.** for each set repeatively. thanks