| Gasoline Tank | |||
| Inlet Pipe | |||
| Needle Valve | Needle Valve Lock Screw | ||
| Air Gate Lever | Throttle Lever | ||
| Clamp Screw | |||
| Screen (Gasoline Strainer) | Air Current | Throttle Stop Screw | |
| Air Intake Gate | Throttle Gate | ||
| Stop Cock | |||
| Cork Float | |||
| Gasoline Inlet Needle | |||
| Sediment Bulb | Feed Pipe | Carburetor Drain Cock | |
| Sediment Bulb Drain Cock | |||
Fig. 149. Ford Fuel System
Q. Why is carburetor adjustment placed on dash?
A. For the convenience of the driver in adjusting the carburetor. After the new car has become thoroughly worked in, the driver should observe the angle of the carburetor adjustment rod at which the engine runs most satisfactorily. In cold weather it will probably be found necessary to turn the dash adjustment one-quarter turn to the left, particularly in starting a cold engine. As gasoline vaporizes readily in warm weather, the driver will find it economical to reduce the quantity of gasoline in the mixture by turning the carburetor adjustment to the right as far as possible without reducing the speed. This is particularly true when taking long drives where conditions permit a fair rate of speed to be maintained, and accounts for the excellent gasoline mileage obtained by good drivers.
Q. What is meant by a “lean” and a “rich” mixture?
A. A lean mixture has too much air and not enough gasoline. A rich mixture has too much gasoline and not enough air. A rich mixture will not only quickly cover the cylinders, pistons and valves with soot, but will tend to overheat the cylinders, and is likewise wasteful of the fuel. It will often choke the engine and cause misfiring at slow speeds, although at high speeds the engine will run perfectly. The mixture should be kept as lean as possible without the sacrifice of any of the power of the motor. A lean mixture will often result in backfiring through the carburetor, for the reason that the gas burns slowly in the cylinder, and is still burning when the inlet valve opens again, which causes the gas in the intake to ignite. A rich mixture is shown by heavy, black exhaust smoke with a disagreeable smell. Proper mixture will cause very little smoke or odor.
Q. How is the carburetor adjusted?
A. The usual method of regulating the carburetor is to start the motor, advancing the throttle lever to about the sixth notch, with the spark retarded to about the fourth notch. The flow of gasoline should now be cut off by screwing the needle valve down to the right until the engine begins to misfire. Then gradually increase the gasoline feed by opening the needle valve until the motor picks up and reaches its highest speed and no trace of black smoke comes from the exhaust. Whenever it is necessary to turn the adjusting needle down more than a quarter turn below its normal position, the lock nut on the top of the carburetor at the point through which the needle passes should first be loosened, as otherwise it is impossible to tell when the needle is turned down in its seat too far. Turning the needle down too tightly will result in its becoming grooved and the seat enlarged. When those parts are damaged it is difficult to maintain proper adjustment of the carburetor. Having determined the point where the motor runs at its maximum speed, the needle valve lock nut should be tightened to prevent the adjustment being disturbed. For average running a lean mixture will give better results than a rich one.
Q. Why does water clog the carburetor?
A. The presence of water in the carburetor or gasoline tank, even in small amounts, will prevent easy starting and the motor will misfire and stop. As water is heavier than gasoline it settles to the bottom of the tank and into the sediment bulb along with other foreign matters. As it is difficult nowadays to get gasoline absolutely free from impurities, especially water, it is advisable to frequently drain the sediment bulb under the gasoline tank. During cold weather the water which accumulates in the sediment bulb is likely to freeze and prevent the flow of gas through the pipe leading to the carburetor. Should anything of this kind happen it is possible to open the gasoline line by wrapping a cloth around the sediment bulb and keeping it saturated with hot water for a short time. Then the water should be drained off. In event of the water getting down into the carburetor and freezing, the same treatment may be applied.