My sons 06 2500 cummins wont start after a cold night unless it's plugged in. Is this the grid going bad? Had pressure test done and replaced an injector last year. It does have a tuner on it. Once it cranks in the am the whole day it will start even after sitting at school Any ideas? ThAnk you in advance.

 

Likely a more worn injectors. We can test them. you can unplug the FCA and see if it helps. Batteries are probably good, but worth checking to make sure they are strong.

 

 

Did you check to see if any codes are showing ?
Turn key on and of 3 times.