[Intrigued]

How's it going with the car, lunarhighway? My Pontiac 6000 had a v-6 diesel, and had TWO batteries to start it with - from the factory. If I did NOT have the block heater plugged in, when below 0 degrees C it cranked slowly - with two good 500+ amp batteries! (10-30 in winter, 30 weight in summer... over a quarter-million miles!!!)

Part of the hard starting trouble when cold is that when the engine block is so cold that the fuel just doesn't get hot enough from the compression to ignite, even with the glow plugs.

I would cycle my ignition a few times when I forgot to plug in my block heater, but once in a while I would have to replace a glow plug. On that car you could read the glow plugs with a voltmeter to see if they were any good. (Would read open or a lot higher resistance - connector to ground - than the others.)

Without the availability of power for a block heater, you may want to go with two batteries, to get the amperage you will need. Maybe larger diameter cables, too... :-)