need a little help, I have a 2003 f-250 with a little less than a 100k miles. I live in central texas where it really doesnt get super cold right now but just noticed that my truck has been hard to start in the mornings. I started to plug it in and was able to get better starts but now for example i had it plugged in all night and went to start it and it would just turn over so i pumped the gas pedal and it would struggle to turn on. It would just pump out black smoke. However once i do get it on and let it run for 30 minutes or so i can turn it and it will crank right up. I have been told it is the glow plugs then that it isnt the glow plugs and that it might be the injectors or glow plug module? Can anybody shed some light on this for me. Keep in mind the last week here has only been about 40 degrees at night and as high as 70 during the day. Thanks in advance