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| Illustration 1 | g00469460 |
Starting and charging system (typical example) (1) Lead to neutral/backup switch for hydraulic pump (2) Ignition switch (3) Neutral start relay (4) Interlock relay (5) Lead for the relay for number two brake (6) Brake/neutral fuse (7) Start relay (8) Fuel shutoff solenoid (9) Main relay (10) Starting aid switch (11) Starting motor solenoid (12) Starting motor (13) Ignition switch fuse (14) Alternator (15) Disconnect switch (if equipped) (16) Battery (17) Breaker for the alternator (18) Starting aid relay (19) Lead to breaker for light circuit (20) Glow plugs | |
The electrical system is a negative ground system. The electrical system operates at 12 volts.
The fuel shutoff solenoid must be energized in order for the fuel to flow to the cylinders.
The charging circuit operates when the engine is running. The alternator circuit produces direct current for the electrical system.
Starting Motor
The starting motor turns the engine flywheel. The rpm must be high enough in order to initiate a sustained operation of the fuel ignition in the cylinders. The maximum average cranking rpm of the starting motor is 130 rpm.
The starting motor should not be engaged for more than 15 seconds. The starting motor should be allowed to cool for at least 30 seconds before the starting motor is engaged again.
The starting motor has a solenoid. The solenoid engages the starter drive in two operations. This process ensures that the starting motor reaches the maximum torque only when the starting motor is fully engaged with the flywheel.
When the engine begins to run, the clutch of the pinion drive prevents damage to the armature that is caused by excessive speeds. The clutch prevents damage by stopping the mechanical connection. However, the pinion will stay meshed with the ring gear until the ignition switch is released. A spring in the clutch returns the clutch to the rest position.
Alternator
The alternator has brushes. The alternator is driven by a belt from the crankshaft pulley. The alternator charges the battery during the engine operation.
The alternator is cooled by an internal fan which is behind the pulley. The fan pulls air through the holes in the front of the alternator. The air exits the rear of the alternator.
The alternator converts the mechanical energy and the magnetic energy into alternating current and voltage. This conversion is done by rotating a direct current electromagnetic field on the inside of a three-phase stator. The electromagnetic field is generated by electrical current flowing through a rotor. The stator generates alternating current and voltage.
The alternating current is changed to direct current by a three-phase, full-wave rectifier. Direct current flows to the output terminal of the alternator. The rectifier has three exciter diodes. The direct current is used for the charging process.
A solid state regulator is installed on the rear end of the alternator. Two brushes conduct current through two slip rings. The current then flows to the rotor field. A capacitor protects the rectifier from high voltages.
The alternator is connected to the battery through the ignition switch. Therefore, alternator excitation occurs when the switch is in the RUN position.
Glow Plugs
Each cylinder has a glow plug which is installed in the cylinder head. When the glow plugs are energized for six seconds, the glow plugs heat the cylinders to approximately 93°C (200°F). This temperature is usually sufficient to heat the fuel for easily starting the engine in cold weather. The glow plugs should not be energized for more than 15 seconds in order to prevent damage to the glow plugs and other engine components.
The glow plugs are electrically operated. The glow plugs are usually controlled by the ignition switch.
Current from the battery heats the tips of the glow plugs. When the glow plugs are energized, the tips of the glow plugs become very hot. The glow plugs improve combustion during cold start conditions.
Fuel Shutoff Solenoid
The fuel shutoff solenoid is mounted to the rear of the fuel injection pump. The plunger of the fuel shutoff solenoid is connected to the fuel rack of the fuel injection pump. When the fuel shutoff solenoid is energized, the fuel shutoff solenoid allows the fuel rack to move to the excess fuel position. When the fuel shutoff solenoid is de-energized, the fuel shutoff solenoid forces the fuel rack to the stop position.