Replaced GPR and still no volts on power side.

I have been having cold start problems and checked the GPR and found it to have voltage of 12.8 on the hot side and zero on the GP side. Bought new one from Ford, replaced it and checked again and same result, zero on the GP side. Now what, have checked through the search and did not find a thread with this issue. Also truck has been missing, enough to throw check engine light, seems to do it more when its raining outside. Had it scanned at Ford and did not happen when there, they said it all seems ok, so no diagnosis, just checking to see if someone has had this issue. 02 7.3 with 260k