Nope they weren't. Before electronics you just had mechanical pumps which squirted fuel into the cylinders at the right time and the heat of compression caused it flash. If your fuel was already jello however it would never even get through the fuel filter ahead of the pump so you had to take measures to keep your fuel flowing. At the truck stops where it gets really cold there are #1 diesel (kerosene) pumps along side the #2 diesel pumps and truckers there mix their own magic proportions of #1 and #2 diesel in their tanks to hopefully keep it liquid.