I have a 79 300d mercedes and live in oklahoma where sometimes the weather is real cold during the winter. Well my battery is fine and everything, I'll even let the glow plug run 3 times before trying to crank it, then I turn the key and it is cranking and everything even with smoke coming out, but the damn thing won't actually start when it's cold outside. What can I do to make it start w/out getting a jump everytime b/c at school it has to stay outside. I need to know, thanks!