M2/M3 BFV ENGINE STARTING/CHARGING SYS - OD1603 - LESSON 1/TASK 1
b.
General Description.
(1) The starting system performs the function of putting the engine into
operation.
The
starting
system
in
today's
vehicles
consists
of
an
electromechanical motor, an electrical storage battery, and, in the case of a
gasoline engine, an ignition system. Diesel engines do not have an engine ignition
system similar to a gasoline engine.
But a diesel engine does have a glow plug
system that preheats a precombustion chamber in the engine cylinders to facilitate
starting the engine in cold weather.
The electro-mechanical motor (known as the starter) is operated by electrical power
furnished by the storage battery. When the vehicle operator turns the ignition key
or presses the ignition button, he is essentially closing the electrical circuit
between the battery and the starter.
Once this electrical circuit is closed,
electric current flows from the battery to the starter, causing it to turn in a
rotary motion. This rotary motion is transmitted by means of shafts and gears to
the engine flywheel, which is connected to the engine pistons by means of a
crankshaft and connecting rods. As the flywheel turns, it causes the pistons to go
through the cycle of intaking and compressing a fuel and air mixture (in a gasoline
engine) which is then ignited by the ignition system. The engine then starts and
operates under its own power.
As soon as the engine starts, the starter disengages from the engine and the
circuit is opened by the operator releasing the ignition key or button. The engine
keeps operating under its own power until the ignition key is turned off. In the
case of a diesel engine, the turning off of the ignition key causes a solenoid to
activate, shutting off the supply of fuel and/or air to the engine cylinders and
causing the engine to stop operating.
To place the engine in operation again
requires repeating the starting procedure just described.
(2) Cranking an engine with an electric starter-motor requires hundreds of
amperes of electrical current, depending on such factors as the size of the engine,
engine horsepower, and weather conditions. The electric current used to crank the
engine must be restored to the battery each time the engine is cranked.
To keep
the battery
4
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