In the old days we got gasoline tractors which handled the cold better. We used lots of ether. we got a 5 gallon bucket of hot water, set it under the oil pan & put a tarp over the hood to make a mini tent & waited 30 minutes. We pulled the gas tractors if we got any one started. We drained the oil every time we parked it, & put warm oil in every time we wanted to start it. For a diesel you can light a fire with a rag or a propane torch & direct the heat into the aircleaner & crank the engine over - this is dangerous but you asked what farmers did/do.
As a fellow Minnesotian with 6 tractors & 5-6 other motor machines, I make sure the machine runs every 4 weeks or the battery is stored in the basement or a charger is put on the battery every 3-4 weeks. I keep the machines in unheated sheds (a month ago when it hit 0 outside, my bigger diesel started right up the next day on summer fuel & summer oil - the shed kept the tractor about 30 degrees for that extra day or two). I try to plug them in, water heater only, when it is below 20 degrees.
Best prep is to change the fuel filter in fall; use a winter grade of oil; use #1 diesel blended 50/50 with #2 plus a bit of fuel additive for cold weather; change the fuel filter in fall; keep the tractor in a shed that will add 5-10 degrees even without heat; have a way to heat it up, electric plug in or a torpedo heater (see the shed helps); make sure your battery & electrical system is in good shape & charge it if your tractor sets more than 7 days in the cold; and change the fuel filter in fall.
In emergency, use a bucket of hot water, direct a hair drier into the air intake, etc. You often only are 5-10 degrees away from getting the starter to spin fast enough (cold oil drag) and adding 100 degrees of heat to the air intake will make a WORLD of difference on the ignition.
Ether is really bad for diesel engines, and can wreck the manifold (explosive shrapnel) with many preheaters but ifyour tractor allows it & you know the issues it can be a neccesary evil for cold starts.
--->Paul
