The oil pressure regulator is located on the body of the pump and connects to the by-pass. It consists of a hollow sleeve screwed into the body of the pump which has a small ball check held by a short coiled spring the tension of which determines the oil pressure. The tension and the pressure may be increased by turning the nut to the right. The nut should not be given more than one turn at a time in either direction as it is very sensitive. A loose main bearing will allow more oil to pass through it. Consequently the pressure registered on the oil gauge will be reduced. This will come about gradually. It is not advisable to attempt to adjust the oil pressure without first noting the condition of the main crank shaft bearings.
The most common cause of failure to operate is the collection of dust and dirt on the sleeve at the lower end of the pump or from an accumulation of sediment back of the ball check. This needs to be cleaned from time to time.
Force and Gravity Oiling System.—The force and gravity oiling system operates in much the same manner as the plunger pump system, except that the oil is pumped into an elevated tank from which it flows through lines by gravity to the various bearings. Oil pumps, however, differ in construction and some manufacturers use eccentric, centrifugal, and gear pumps. Oil pumps are very simple in construction and action and can be readily understood by recalling their functional action.
Oil pumps rarely give any trouble, and if they fail to function properly, dirt should be immediately suspected, and the ball valves and pipes inspected and cleaned.
CHAPTER IV
BRIEF TREATISE ON CARBURETION
A carburetor is a metering device whose function is to mechanically blend liquid fuel with a certain amount of air to produce as nearly a homogeneous mixture as possible, and in such proportions as will result in as perfect an explosive mixture as can be obtained.
If a gas is used as a fuel it is of course not so difficult to obtain a homogeneous mixture due to the intimacy with which a gas will mechanically mix with air. This intimacy is a result of the minuteness of the molecules of both the gas and the air. With a liquid fuel, such as gasoline, however, it is quite different, especially with low test gasoline. If it were possible to completely transfer the liquid fuel into its vapor the latter would act as a gas and would, therefore, mix with the air to form a homogeneous mixture. It should be, and is, therefore, the aim of the carburetor designer to produce an instrument which will atomize the fuel and break it up into small particles so that every minute particle of the fuel will be surrounded by a correct proportion of air when it is discharged into the intake manifold of the motor. To facilitate the vaporization of these minute particles of fuel it is advisable to preheat the air taken into the carburetor, thereby furnishing the necessary heat units required to vaporize the fuel by virtue of its physical property known as its latent heat of evaporation.
There is a range of proportions of air to vapor, for a given fuel, between which combustion will obtain. This range extends from that proportion known as the upper limit of combustion to that known as the lower limit of combustion. The upper limit is reached when the ratio of air to vapor is a maximum at which combustion will take place; that is to say, any addition of air in excess of this maximum will render the mixture non-combustible. The lower limit is reached when the ratio of air to vapor is a minimum at which combustion will take place, any decrease of air below this minimum producing a non-combustible mixture. It should be remembered that the limits of combustion of any fuel with air are dependent upon the temperature and pressure.
| Carburetor Flange | Throttle Valve | ||||
| Throttle Stem or Shaft | |||||
| Large Venturi | Idle Discharge Jet | ||||
| Idle Adjustment Needle | |||||
| High Speed Adjustment Needle | |||||
| Small Venturi | Float Needle | ||||
| Air Bleeder | |||||
| Mixture Control Valve or Choker | |||||
| Float | |||||
| Accelerating Well | |||||
| Idling Tube | Strainer | ||||
| Float Needle Seat | |||||
| High Speead Needle Seat | |||||
| Strainer Body | Gasoline Connection | ||||
| Drain Plug | |||||