Ford Manual/The Gasoline System
This cut illustrates the principle of Ford Carburetion. (Cut No. 7)
The Gasoline System
| The Carburetor—how does it work? | Answer No. 42 |
The carburetor is of the automatic float feed type, having but one adjustment—the gasoline needle valve. The cross-section diagram of carburetor on page 20 shows how the gasoline enters the carburetor, is vaporized by a current of air and passes through the inlet pipe to the engine in the form of an explosive mixture. The gasoline, entering the bowl of the carburetor, gradually raises the float to a point where the inlet needle is forced upwards into its seat, thus cutting off the flow of gasoline. As the gasoline in the bowl recedes, the float lowers, allowing the needle to drop from its seat and the flow of gasoline is resumed. It is plain to see that a constant level of gasoline is maintained in the carburetor by the automatic action of float and needle. The quantity of gasoline entering into the mixture is governed by the needle valve (see Answer No. 45). The volume of gas mixture entering the intake pipe is controlled by opening and closing the throttle, according to the speed desired by the driver.
| Why is Carburetor adjustment placed on dash? | Answer No. 43 |
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 adjusting 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 speed. This is particularly true when taking long drives where conditions permit a fair rate of speed being maintained, and accounts for the excellent gasoline mileage obtained by good drivers.
| What is meant by a "lean" and a "rich" Mixture? | Answer No. 44 |
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 carbon, 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 machine 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.
| How is the Carburetor adjusted? | Answer No. 45 |
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 spied 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 top of the carburetor at the point through which 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 these 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.
| Why does water clog the Carburetor? | Answer No. 46 |
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 matter. 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 gasoline 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 the water gets down into the carburetor and freezes, the same treatment may be applied.
| What makes the Carburetor leak? | Answer No. 47 |
The flow of gasoline entering the carburetor through the feed pipe is automatically regulated by the float needle raising and lowering in its seat. Should any particle of dirt become lodged in the seat, which prevents the needle from closing, the gasoline will overflow in the bowl of the carburetor and leak out upon the ground.
| When there is dirt in the Carburetor—what? | Answer No. 48 |
The spraying nozzle of the carburetor having a very small opening, a minute particle of grit or other foreign matter will clog up the orifice, and result: motor will begin to misfire and slow down as soon as it has attained any considerable speed. This is accounted for by the fact that at high speeds the increased suction will draw the particles of dust, etc., into the nozzle. By opening the valve needle half a turn and giving the throttle lever two or three quick pulls the dirt or sediment will often be drawn through, when the needle may be turned back to its original place. If this does not accomplish the purpose, the carburetor should be drained.
| If Engine runs too fast or chokes with throttle retarded—what? | Answer No. 49 |
If the engine runs too fast with throttle fully retarded unscrew the carburetor throttle lever adjusting screw until the engine idles at suitable speed. If the motor chokes and stops when throttle is fully retarded the adjusting screw should be screwed in until it strikes the boss, preventing the throttle from closing too far. When proper adjustment has been made, tighten lock-screw so that adjustment will not be disturbed,
| What is the purpose of the Hot Air Pipe? | Answer No. 50 |
It takes the hot air from around the exhaust pipe and conducts it to the carburetor—where the heat facilitates the vaporising of the gasoline. It is usually advisable to remove this pipe in the hot season—but it is an absolutely necessary feature during cold weather.
| What is the purpose of the Cork Float? | Answer No. 51 |
It automatically controls the flow of the gasoline into the carburetor. If it floats too low, starting will be difficult; if too high, the carburetor will flood and leak. A cork float which has become fuel soaked should be removed and replaced by a new one or thoroughly dried and then given a couple of coats of liquid shellac to make it waterproof.
| Should Priming Rod be used in starting when Motor is warm? | Answer No. 52 |
No. The carburetor does not ordinarily require priming when the motor is warm, and starting with the rod pulled out is apt to "flood" the engine with an over-rich mixture of gas, which does not readily explode. This naturally causes difficulty in starting. If you should accidentally flood the engine, turn the carburetor adjusting needle down (to the right) until it seats; then turn the engine over a few times in order to exhaust the rich gas. As soon as the motor starts, turn back the needle (to the left) and readjust the carburetor.