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Q. What steps are necessary to find out if fuel supply system is responsible for the stop?

A. The amount of gasoline in the tank may be easily ascertained by inspection and if there seems to be enough the next thing to do is to uncouple the gasoline pipe at the carburetor after shutting off the valve at the bottom of the tank and then to note if a stream of fuel the full size of the orifice issues from the pipe when the gasoline shut-off valve is again open. If the gasoline does not flow it indicates that the pipe is stopped up. If the gasoline seems to be reaching the carburetor in proper quantities, the next point is to see if the spray nozzle is clogged up. A little gasoline is injected into the cylinders through the spark plug holes or the compression relief pet cocks and the motor is cranked over with a switch in place. If the motor starts and runs for a few revolutions it may be taken as an indication that even though the gasoline reaches the carburetor it does not reach the cylinders and the only defect that will prevent the gasoline from going into the mixing chamber is either dirt in the spray nozzle or in the passage between the spray nozzle and the float chamber. With carburetors of the adjustable spray nozzle type, dirt may often be cleared from the spray nozzle by screwing the gasoline regulating needle valve to its seat and then returning it to its running position. If that fails to clear the stand pipe the carburetor must be taken apart and thoroughly cleaned.

Q. Do oil or water systems fail without warning?

A. The lubricating or cooling systems are not apt to fail suddenly and motor stoppages due to either defective cooling or lubrication are rare because a failure in either of these groups will make itself evident some time before a motor actually stops because it has overheated or the parts seized through lack of lubrication.

Q. What should be looked for if an engine has no power but is running steadily?

A. If an engine is slowing down gradually and yet continues to explode regularly, this indicates either faulty lubrication or cooling.

Q. What should be looked for if engine loses power because of misfiring?

A. If an engine loses power on account of irregular operation or lack of regular sequence of explosions a number of defective conditions in carburetion, ignition or in the mechanism of the motor itself may be responsible for the faulty operation. These troubles are considered at length in the next lesson.

Q. What would cause a sudden knocking noise?

A. A sudden knocking or pounding noise from the interior of the motor usually indicates a loose or broken part.

Q. What would cause a gradually increasing knock?

A. If a motor is overheating because of faulty cooling or insufficient lubrication this condition will be evidenced by a knock or pound which will increase as the motor gets hotter. A gradually increasing knock is also sometimes caused by driving up an incline with the spark lever too far advanced.

Q. What parts of power plant produce knocking?

A. Worn or loose bearings on the crank shafts or connecting rods are the usual causes of knocking. Carbon deposits in the combustion chamber also cause preignition, which is evidenced by pounding.

Q. What does a loud squeak indicate?

A. A loud squeak is usually produced by a dry bearing and the car should be stopped as soon as a noise of this nature is heard and a search made to locate the cause.

Q. What does a loud hissing noise indicate?

A. A hissing noise shows a leak in the combustion chamber and is sometimes caused by a cracked or broken spark plug porcelain, a loose insulator in a spark plug, or a compression relief pet cock has either jarred open or the small spigot member or plug has dropped out of its center allowing the gases under pressure to escape.

Q. What does a noisy exhaust show?

A. A noisy exhaust shows a leak around the exhaust manifold or a disconnected muffler pipe if the cut-out valve is not open.

Q. What does steam coming out of the radiator indicate? A. If a radiator is steaming it indicates that the motor is over

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heating. This may be due to lack of water in the cooling system or to defective lubrication.

Q. Is steam always a sign of serious trouble?

A. Steam from the radiator does not necessarily indicate serious trouble because if the motor has been run continuously for some time on one of the lower gear ratios as in hill climbing it may

heat up enough to cause the water to boil and no serious injury will result if the supply of water in the radiator is augmented with cooler water. Driving on a retarded spark will also cause the radiator to steam as will a broken fan belt or excessively rich mixture.

Q. What does a rattling noise indicate?

A. A rattling sound is generally produced by some loose part of the chassis, which has become partially free of its restraining bolts or fastenings but which is still in place because it is held by some other member. Rattling noises are generally caused by loose mud guards, brakes or various operating rods extending from the operating levers or pedals to the parts they actuate.

Q. Suppose the car stops and the rear wheels do not turn, but the motor continues to run and the gear shift lever is in its proper position, what should be looked for?

A. The first thing to see is that the clutch is not slipping as very often the interlock between one of the brake levers and the clutch shifter will hold the clutch out of engagement if the brake lever is only partially applied or if adjustments have just been made. The clutch may be engaged properly but yet the connection between the clutch and the gearset may be broken. The gear lever may be in operative position but a pin may have sheared off so that the gears in the transmission case always remain in neutral position and do not shift or change positions when the speed lever is moved.

Q. Suppose the motor operates correctly and the gears in the gearset are turning, but the car does not move, where is the trouble apt to be?

A. Under the conditions stated the defect would exist in the driving mechanism at some point. A pin or driving key may have

sheared off in the universal joint or bevel drive pinion or the propeller shaft may have become broken. The adjustment of the bearings holding the differential case may have loosened up so the ring gear has moved over out of engagement with the driving pinion. The rivets or bolts holding the ring gear to the differential case may have sheared off so that the gear is turning without producing movement of the differential casing. One of the driving shafts may have broken in the axle housing between the differential and the wheel hub or a hub cap on a full floating hub may have come off and allowed the driving shaft clutch to come out of engagement with the corresponding member on the hub. The troubles enumerated are uncommon, however, though they have occurred often enough to warrant suspicion if the condition outlined should materialize.

Q. Suppose the car does not run freely down hill with the power shut off and the clutch released, what is the trouble?

A. This may be taken as an indication of binding or undue friction in the wheels or driving system. The most common cause is binding brakes because they are adjusted too tightly.

Q. What is the trouble when a car jumps or runs in irregular spurts?

A. This trouble is often caused by the motor running unsteadily or misfiring and then running on all cylinders for a time relaxing again into the condition of irregular operation where only part of the cylinders are working. If the engine is running steadily this jumping may be due to a partially slipping clutch which transmits the power correctly at times and does not take hold properly at other times.

Q. What should be looked for if gears do not shift well?

A. If trouble is experienced in shifting gears one should examine the clutch to see if this member releases promptly and does not spin. Sometimes the gear teeth may have become burred and will not engage properly or the defect may be due to wear or binding in the connection between the gear shift lever and the sliding gear actuating fork.

Q. What is the reason when a car does not stop promptly? A. If a car does not stop within a reasonable time after the clutch lever is released and the brake applied it signifies that the brakes are not holding as well as they should and that they either need readjustment or renewal of the frictional material.

Q. What is at fault if a car starts forward suddenly as soon as clutch is engaged?

A. If the car jumps forward with the clutch pedal let in gradually it means that the clutch is engaging too harshly and that there is lack of resiliency in the clutch facing if a cone type is used or lack of oil in a multiple disc form

Q. What does erratic steering indicate?

A. If trouble is experienced in steering the car and the steering wheel works freely there are two points that demand immediate inspection. The first thing to do is to make sure that the tie-bar joining the steering spindle arms is not loose or detached at one end and that the drag link and steering arms are also properly joined together. The second point to be examined and the most common trouble is a deflated front tire. Erratic steering is sometimes caused by a defect of the differential gear which prevents it from functioning properly.

Q. What does a loud explosion indicate?

A. A blowout in either front or rear tires is generally evidenced by a loud pop which may sound in some cases like a gun shot. It is due to the sudden escape of air confined under high pressure to the outer air and the noise is produced by the same cause as when an inflated paper bag is suddenly broken.

Q. What does “bumping” indicate?

A. “Bumping” is a sure indication of a flat tire on the rear wheels or a broken spring.

Q. What happens if one continues to run a car on a flat tire?

A. The outer casing and inner tube will be destroyed and the rim may be badly dented. In forms of tires of the straight wall type and in some quick detachable forms as soon as a tire becomes deflated it is liable to come right off of the wheel, as the air pressure is an important factor in holding it in place against the restraining rim member.


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