Greetings and Salutations.

On 22 Jan 2005 08:03:28 -0800, jim rozen
wrote:

In article 42, notreallyme
says...

... Diesel engines are fire pistons!


In a way yes they are, but don't they need a battery to work, as in 'glow
plugs'?

Yes, but only for starting. Once running the glow plugs are
switched off, right?

Jim


Actually...not really. A diesel engine ignites the fuel/air
mixture purely by compression. Now...most, if not all, of them have
glow plugs that are used to help the process get started when the
engine temperature is low enough that even the massive compression
of the diesel engine is not enough to get the air/fuel mixture up
above the ignition temperature. A glow plug, by the by, is really
nothing more than a small heating element that sticks into the
cylinder and heats up to red-hot for a few moments when the engine
is first started. This extra heat is enough to ensure that combustion
will start, and, once the engine runs for a few minutes, it will have
warmed up enough that the ignition is self-sustaining.
Typically, glow plugs are set to run for no more
than a minute or so (although their real usefulness ends after
the first ignition in the cylinder).
It is perfectly possible to start a diesel engine
without working glow plugs. As long as the block is warmed
a little bit, the engine will fire up. Most large diesel
engines come with a 1 kw heater element that screws into
the block (typically by the oil filter), and is plugged
into 110v to keep things heated up. I am reduced to this
myself, as my truck currently has some issues with the glow
plug circuitry, and, without the block heater, it just won't
fire off below about 35 degrees.
Regards
Dave Mundt