Starting System


Since the engine is not capable of starting by itself, it requires external power to crank it and help it start. Among the various means available, automobiles now use an electric motor that has been combined with a magnetic switch that shifts a rotating pinion gear into and out of mesh with the ring gear on the circumference of the engine flywheel.
The starter motor must generate a large torque from the limited amount of power available from the battery. At the same time, it should be light and compact. For these reasons, a DC (direct current) series motor is used.
The engine is not completely started until it can continuously repeat its operational cycle of intake, compression, combustion, and exhaust strokes on its own. The first step for starting the engine, then, is to crank the engine and induce the initial combustion cycle. The starter motor must therefore be at least capable of cranking the engine at the minimum rotational speed that is required to induce initial combustion.
Starter Motor
The starter motor is a small but powerful electric motor that delivers a high degree of power for a short period of time. When the starter motor is energized it engages the flywheel ring gear and produces torque, which turns the flywheel and cranks the engine.
When the driver releases the ignition switch from the start position to the run position, the solenoid is deactivated. Its internal return springs cause the drive pinion to be pulled out of mesh with the flywheel, and the starter motor stops.


Universal Ignition Switch
 The ignition switch allows the driver to distribute electrical current to where it is needed. There are generally 5 key switch positions that are used:
Lock- All circuits are open ( no current supplied) and the steering wheel is in the lock position. In some cars, the transmission lever cannot be moved in this position. If the steering wheel is applying pressure to the locking mechanism, the key might be hard to turn. If you do experience this type of condition, try moving the steering wheel to remove the pressure as you turn the key.
Off- All circuits are open, but the steering wheel can be turned and the key cannot be extracted.
Run- All circuits, except the starter circuit, are closed (current is allowed to pass through). Current is supplied to all but the starter circuit.
Start- Power is supplied to the ignition circuit and the starter motor only. That is why the radio stops playing in the start position. This position of the ignition switch is spring loaded so that the starter is not engaged while the engine is running. This position is used momentarily, just to activate the starter.
Accessory- Power is supplied to all but the ignition and starter circuit. This allows you to play the radio, work the power windows, etc. while the engine is not running.
Most ignition switches are mounted on the steering column. Some switches are actually two separate parts;
The lock into which you insert the key. This component also contains the mechanism to lock the steering wheel and shifter.
The switch which contains the actual electrical circuits. It is usually mounted on top of the steering column just behind the dash and is connected to the lock by a linkage or rod.

Neutral Safety Switch
This switch opens (denies current to) the starter circuit when the transmission is in any gear but Neutral or Park on automatic transmissions. This switch is normally connected to the transmission linkage or directly on the transmission. Most cars utilize this same switch to apply current to the back up lights when the transmission is put in reverse. Standard transmission cars will connect this switch to the clutch pedal so that the starter will not engage unless the clutch pedal is depressed. If you find that you have to move the shifter away from park or neutral to get the car to start, it usually means that this switch needs adjustment. If your car has an automatic parking brake release, the neutral safety switch will control that function also.


Familiarize Starter Relay

  1.  Remove and Disconnect Starter Relay
  2. Apply battery voltage to C and D terminals of relay
  3. Check continuity between A and B terminals of the relay. it should exist.
  4. Disconnect batterry voltage, there should be no continuity between A and B terminals of the relay
  5. If relay does not operate as specified, replace relay
A relay is a device that allows a small amount of electrical current to control a large amount of current. An automobile starter uses a large amount of current (250+ amps) to start an engine. If we were to allow that much current to go through the ignition switch, we would not only need a very large switch, but all the wires would have to be the size of battery cables (not very practical). A starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current flow from the battery to the starter. The starter solenoid in some cases also mechanically engages the starter gear with the engine.


Before discussing the preventive maintenance and diagnostic procedures for the starting system, were going to cover certain environmental and product application factors that can cause the starting system to malfunction.

Battery charge
 A battery having a low / poor state of charge will place abnormal stresses on the starting system. When measuring battery voltage, make sure voltage is 12.4 V or greater.

Excessive heat
A starter motor can become damaged if it operates too long at high temperatures. Excessive heat is generally due to continuous engagement of the starter. Damage to starting system components can occur when the starter motor is cranked for long periods (often due to cold weather starts, improperly tuned engine, etc.). Starter should operate for 30 seconds maximum then let to cool down for 2 minutes.
Excessive vibration
If starting system components are poorly or loosely mounted to the vehicle�s engine, the resulting vibration can damage sensitive internal components.
Corrosion, dirt, and dust
Starting system components operate less efficiently when corrosion forms or dirt particles build up around wire and cable connection points. Corroded and dirty connection points impair the flow of electrical current.
Improper use of starting fluid. Overuse and / or extended use of starting fluid places abnormal stresses on starting system components.
Defective solenoid
If the starter fails to engage or fails to stay engaged, the pull-in or hold-in coil may be defective, or the wiring to the solenoid is bad. You need to check the wiring to the solenoid. If the wiring is ok then the coil is defective and you will have to replace the solenoid.

Battery cables are large diameter, multi stranded wire which carry the high current (250+ amps) necessary to operate the starter motor. Some have a smaller wire soldered to the terminal which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns, this indicates a high resistance in the heavy cable. Care must be taken to keep the battery cable ends (terminals) clean and tight. Battery cables can be replaced with ones that are slightly larger but never smaller.

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