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Q. How should motor be cranked?
A. The method of cranking the motor properly is outlined at Fig. 248. In the first place the starting handle should be grasped in the hand as indicated in the inset A because if held in this manner it will be pulled out of the hand if the motor should back fire due to an advanced spark lever and early explosion. In cranking the motor the starting handle should always be pulled up with a quick, sharp movement. One should never push down on a starting handle, because when one pulls if there is a reversal of crankshaft motion
Right way of cranking the motor
Wrong way of cranking the motor
Fig. 248.—Proper Method of Grasping Hand Starting Crank in Order
to Avoid Injury Due to Backfire.
the starting crank will be pulled out of the hand, whereas if one pushes down a back kick is apt to injure the arm or wrist.
Q. Describe process of “tickling" carburetor and explain why this is sometimes necessary.
A. After a carburetor has been standing for a time a certain portion of the liquid in the float bowl is apt to evaporate or leak out and the level of fuel will be so low in the standpipe that gasoline will not be drawn out to start the motor. In order to insure having sufficient gasoline in the mixing chamber it is customary to depress the float several times with a small priming pin or plunger protruding through the float bowl cover. This process is commonly called “tickling” the carburetor and causes a portion of the gasoline to overflow the standpipe so when the air is sucked through the mixing chamber it picks up some of the liquid fuel and a rich mixture is produced that makes starting easy. Depressing this pin is sometimes called "priming" the carburetor.
Fig. 249.—Showing Various Positions of Motor Control Levers for
Different Engine Speeds.
Q. What is another method of priming the engine with fuel?
A. With most types of motors, starting will be considerably facilitated on a cold morning or after the car has been standing for a time if gasoline is introduced directly into the cylinders through the priming cocks or compression relief cocks on the cylinder heads.
Q. What is the first step after the engine starts, and why is it necessary?
A. As soon as the engine starts, the throttle lever should be pulled back until the throttle is almost closed in order to prevent the engine "racing."
Q. What is the objection to engine racing?
A. If a motor runs at high speeds while the car is not in motion it will be subjected to unnecessary wear and the car will vibrate unduly.
Q. How is engine speed controlled ?
Fig. 250.—Motor and Car Control Group of Pope-Hartford Car.
and throttle levers, as shown at Figs. 247-C, 249, and 250. In most cars the spark and throttle levers are carried above the steering wheel where they may be easily reached, though sometimes they are mounted on the steering column, as shown at Fig. 249. As a rule, advancing the spark and giving the engine more gas by moving the throttle lever will accelerate motor speed, while retarding the spark and cutting down the supply of gas will slow the engine down. The various positions of the spark and throttle levers of the Pierce-Arrow car for starting, slow, medium and fast running are indicated at Fig. 249.
Q. Describe an automatic engine stop to prevent excessive speed.
A. Some forms of engines are provided with a governor connected with the throttle in such a way that when the engine speed exceeds a certain predetermined point the throttle will be closed by the governor and the engine speed will slacken automatically.
Q. Outline common method of cutting out governor action. A. In cars where a governor is fitted on the engine the
lever or a foot accelerator may be used to open the throttle independently of the governor so that this member will only be operative when the throttle lever or accelerator pedal is set for low or medium speeds.
Q. Why should spark be advanced after engine is started?
A. The spark lever should be moved from the retard position as soon as the engine is started in order to bring the ignition point so the spark takes place just when the piston reaches the end of its compression stroke instead of after it has started to go down on the power stroke. Continuous operation with lever in retarded position will mean overheating and loss of engine efficiency.
Q. What happens if spark lever is too far advanced?
A. If the engine is run with the spark lever advanced too much, the charges will explode before the piston reaches the end of its compression stroke and this preignition, or early explosion, will impose stresses on the motor bearings and will produce a pronounced knocking sound because it tends to oppose piston movement.
Q. What is the best position for spark lever under average running conditions?
A. The spark lever can be placed to best advantage at that point on the segment which corresponds to ignition when the piston reaches the end of the compression stroke, because this condition is one favorable to efficient engine action and makes possible very flexible control by throttle lever alone. In some cars using magneto ignition no provision is made for advancing or retarding the time of the spark which is set so it occurs slightly in advance of top center, or when the piston has just compacted a charge of gas and is ready to descend on its power stroke. In cars using this system of control the engine speed is regulated entirely by the throttle lever or accelerator pedal.
Q. What should be done if any unusual noises materialize after engine is started?
A. If any unusual sounds are heard after the engine is started the operator should immediately stop the motor and investigate the cause of the noise. Sometimes considerable damage may be done to the mechanism by a loose or broken part if the engine is kept running when a defective condition has made itself known.
Control see "The Modern Gasoli
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