The battery stores chemical energy that can be
changed into electrical energy. When the driver turns igni-
tion switch (start switch), the solenoid (high-current relay)
sends battery current to the starter motor. The starter
motor has a small gear that engages a large gear on the
crankshaft flywheel. The motor has enough torque (turning
force) to spin the flywheel, and thus the crankshaft, until
the engine starts and runs. Then, the driver releases the
ignition key and deactivates the starting system.
20 Auto Engine Repair
Hot coolant
Water
pump
Engine
water
jacket
Crankshaft pulley
Fan belt
Cooled
coolant
Airflow to
remove heat
from coolant
Fan
Radiator
Figure 1-21. A cooling system is needed to remove heat from
the engine and prevent severe engine damage. Water jackets
allow coolant to flow around the cylinders and through the
cylinder head. A water pump circulates coolant through the
system. The radiator dissipates heat into the outside air. A fan
pulls air through the radiator. (DaimlerChrysler)
Oil
dipstick
Oil to crank
and camshaft
Oil pump
Oil gallery
Oil filter
Oil to
valve train
Oil pan
Figure 1-22. The lubrication system prevents excess friction
that may damage the engine. Note the part names.
(DaimlerChrysler)
Combustion
Spark
plug
Spark plug
wire
Ignition coil
Battery
Electronic
control unit
or switching
device
Speed sensing
device or
pickup coil
Trigger wheel
Figure 1-23. The ignition system is used on a gasoline engine
to ignite the fuel in the combustion chamber. A coil produces
high voltage for the spark plug. When the switching device
breaks the flow of current to the coil, the coil and spark plug fire
to ignite the fuel.
Main fuse
Wiring harness
Flywheel
ring gear
Starter solenoid
Starter cable
Starter motor
Ignition
switch
Positive
battery
cable
Negative or
ground
cable
Figure 1-24. The starting system rotates the crankshaft until the
engine starts. A powerful electric starter motor has a gear that
meshes with the gear on the engine flywheel. A solenoid makes
the electrical connection between the battery and the starter
motor when the ignition key is turned to the start position.(Honda)