Originally posted by makakio
I was told you wait until the plugs are lit and hot to keep from dumping huge amounts of fuel into the cylinders while cranking and waiting for the plugs to get hot enough to ignite (on the assumption that starting your car with a big BANG in every cylinder is typicallly bad for it). The excess would explain the smoke - perhaps this is all about air quality rather than longevity though...
Diesel is a compression ignition system. Therefore, it works on the simple concept that when air molecules are compressed, they heat up due to the friction produced by the molecules rubbing against each other under high pressure, thereby producing enough ambient heat to ignite the diesel fuel. If I remember correctly, diesel fuel will not ignite until heated to 148-185°F.
The glow plugs are merely an assist, whereby they pre-warm the air in the prechamber prior to compressing it. They do not ignite the fuel itself, they simply warm the air to assist in the compression-ignition process.
The smoke is, in fact, simply unburned diesel fuel combined with the soot of the inefficiently burning fuel that has finally ignited.
And every internal combustion engine starts, "with a big BANG in every cylinder", everytime you start it, then it continues to do the same thing over and over again, just faster as you add more fuel and air...
Saka sama to ishiro muki...