I just bought a 1991 GMC Suburban with a 6.2 diesel. The previous owner said it has a problem with the charging system. He said it was marginal when it was warmer out(45*F) and doesn't work at all when it gets really cold(10*F). The alternator was checked and passed. I think its either the voltage regulator or the battery cables.
I'd say it is the battery. It might check good when it is warm but not work at all when it is cold. A bad regulator and cables might cause it to amplify the problem when it is cold though. I'm in Alaska and I have a 99 Tahoe with a 5.7. When it got below 20f she was hardly starting. The battery was green and when I put it on the charger and tested it the battery was fine. I have a brand new Alt. and the cables are good. I decided to replace the "good" battery. Problem is now gone. It starts like a champ at -20f.
working in a dealership i can tell you, the "green" indicators on the battery are crap, 90% of the indicators dont work, car wont start but damn... the indicator sure is green!!
How many CCAs will it need? I saw a guy on youtube trying to start a 1982 Chevy pickup with a 6.2 diesel. He's got two 950cca batteries in it and I'm pretty sure thats too much. I've never seen a 6.2 crank so fast.
I'm not sure on the CCA's but your local battery shop can tell you what will fit. Since you are in a cold climate like myself, get a battery with a little more CCA's than stock. You can also parallel to batteries but you don't need it unless you are using stuff like a winch. In the end I installed a Interstate battery in my 1966 and have had no problems with it. My Energizer didn't last 3 years. I'm so happy with my Interstate that I put one in my 1999 Tahoe when she was getting hard to start.
