Glow Plug Issues
 

I have a 2007 6.0 power stroke that just all of the sudden started having issues staring when cold. It has had problems for along time that I believe are due to the injectors. However now it almost will not start unless it has been plugged in if it is below 40 degrees out. I pulled it in my shop the other night and put the scan tool on it and found that I had a bunch of codes related to the glow plugs. P0671, 0672 and so on. The only cylinders that were missing were 6 and 7. I searched around and found how to test the plugs using the connector for the glow plug harness. I did so and every cylinder checked between 0.7 and 1.4 ohms. So that checked out ok. After reading a lot of stuff about the issue, if the plugs checked good almost every person had to replace the GPCM. So I did so. I cleared the codes in the computer and tried it all out again. I wasn't able to actually try to start the truck at that point as it was already warm and I figured that the plugs may not even need to turn on anyway. But I did run a code scan again and got the same codes again. I am not sure what to check next or where to look. I haven't really found much else online that tells much about troubleshooting beyond that point. If anyone could at least point me in the right direction it would be helpful.

Don't know if any of this matters but I am also getting a P0275 Cylinder 5 contribution fault, which I think has to do with the injector since when I test my injectors when it is cold it is the only one I turn off that doesn't change the way the engine is running? Also I get a P0487 EGR Throttle position etc. and this would likely be due to the EGR delete? And finally I have a P0611 FICM Performance, which I suppose could be due to the higher voltage FICM board I installed a few years ago?

Just FYI also about a year ago I put new head gaskets and studs in the truck, along with a blue spring deal in the fuel regulator, the EGR Delete and a few other minor things. I couldn't afford to do the injectors with all the other stuff I did then so I have just been living with that. Truck for the most part runs great except that it is a little rough at first when it is cold out.

Thanks in advance.

ONE MORE THING
 

I have always ran Rotella T-6 5w-40. I also use Rev-x which does seem to help the injectors. But honestly that isn't my problem currently.

I did forget to mention that I checked the wiring harness side of the plugs for the glow plugs, and they show 10.5 or so volts all the time. They go up to around 12 when you turn the truck on but never go below around the 10.5. But they don't seem to affect my batteries at all. I don't know a ton about the electrical side of the engine so I don't know what is supposed to go on there, but I would guess they should not have voltage unless they are supposed to be on.