VACUUM SYSTEMS
CONSTRUCTION, OPERATION AND CARE
The vacuum systems have proved to be one of the important inventions
pertaining to successful motor operation. They are self contained,
simple in construction and automatic in operation. They do away with
the troublesome power and hand pressure pumps and their connections.
[Illustration:
AIR VENT
FROM INTAKE MANIFOLD
FROM GASOLINE SUPPLY TANK
Fig. 50. Vacuum System--Top Arrangement]
Fig. 50 shows the top arrangement and connections. R is the air vent
over the atmospheric valve. The effect of this is the same as if the
whole tank were elevated, and is for the purpose of preventing an
overflow of gasoline, should the position of the car ever be such as
to raise the fuel supply tank higher than the vacuum tank. D shows the
pipe connection from the fuel supply tank. C shows the pipe connection
to the intake manifold. W shows a tap or vent through which gasoline
may be fed into the upper chamber, in case the fuel supply tank is
damaged or put out of commission. R shows the air vent connection from
the lower tank.
Fig. 51 shows a general diagram of vacuum system installation. One of
the chief advantages is that it allows the carburetor to be placed
near the head of the motor and does away with the long manifold
connections required with the gravity feed systems. This also reduces
the frictional resistance, gives a richer mixture and greater volume of
flow.
[Illustration:
AIRVENT
A--CONNECTION
BETWEEN INTAKE
MANIFOLD AND
VACUUM TANK
C--CONNECTION
FROM VACUUM
TANK TO CARBURETOR
B--CONNECTION
BETWEEN
MAIN GASOLINE
SUPPLY TANK AND
VACUUM TANK
Fig. 51. Vacuum System Installation]
Fig. 52 shows a sectional view of the Stewart Vacuum System and
explains the operative value of each part. A is the suction valve for
opening and closing the connection to the manifold through which a
vacuum is extended from the engine manifold to the gasoline tank. B is
the atmospheric valve, and permits or prevents an atmospheric condition
in the upper chamber. When the suction valve A is open and the suction
is drawing gasoline from the main supply tank, the atmospheric valve B
is closed. When the suction valve A is closed, the atmospheric valve
B must be open, as an atmospheric condition is necessary in the upper
tank in order to allow the gasoline to flow through the flapper valve
H into the lower chamber. C is a pipe connecting the tank to the
intake manifold of the engine. D is a pipe connecting the tank to the
main fuel supply tank. E is the valve control lever and has two coil
tension springs S attached to operate the short valve lever F. G is the
metallic air-containing float, which controls the action of the valves
through the spring and lever arrangement. H is the flapper valve at the
outlet of T, and it closes by suction when the vacuum valve A is open.
When the vacuum valve A closes, the atmospheric valve B opens and
relieves the suction in the upper tank, the flapper valve H opens and
allows the fuel to flow from the upper tank into the lower chamber.
[Illustration:
AIR VENT
TO INTAKE
PASSAGE
FROM
GASOLINE
TANK
FLOAT VALVE
UPPER
CHAMBER
LOWER
CHAMBER
TO CARBURETOR
Fig. 52. Vacuum System Diagram--Stewart Warner]
J is a plug in the bottom of the tank which can be removed to clean or
drain the tank. This plug can be removed and replaced with a pet-cock
for drawing off gasoline for priming or cleaning purposes. K is the
line to the carburetor. It is extended on the inside of the tank to
form a pocket for trapping water and sediment. L is a channel space
between the inner and outer shells and connects with the air vent R,
thus admitting an atmospheric condition to exist in the lower chamber
at all times, and thereby permitting an uninterrupted flow of gasoline
to the carburetor. R is an air vent over the atmospheric valve; the
effect of this valve is the same as if the whole tank was elevated. It
is also for the purpose of preventing an overflow of gasoline should
the position of the car ever be such as would raise the fuel supply
tank higher than the vacuum tank. Through this tube the lower or
reservoir chamber is continually open to atmospheric pressure. T is the
outlet at the bottom of the float chamber in which the flapper valve H
is located. U is the float stem guide. V is a strainer which prevents
foreign matter from passing into the vacuum chamber. W is a tap or vent
through which gasoline may be fed into the upper chamber if the fuel
tank is damaged or put out of commission.
The simple and durable construction of this system makes it unlikely
that the car owner will ever need to make internal repairs. Before
attempting to repair this tank make sure that the trouble is not due to
some other cause.
=Air Vent.=--A small amount of gasoline may escape through the air
vent occasionally. This will do no harm and no adjustment is needed.
However, if the vent tube continues to overflow, one of the following
conditions will be responsible: 1. The air hole in the main supply tank
is stopped up, or the hole is too small. Enlarge the hole or clean it
out. 2. If gasoline leaks from the system except from the vent tube,
it can only do so from one of the following causes: a. A leak may exist
in the outer wall of the tank. If so soldering it up will eliminate the
trouble. b. The carburetor connection on the bottom of the tank may be
loose. c. There may be a leak in the tubing at the head of the tank. d.
The cover of the tank may be loose.
=Failure to Feed Gasoline to the Carburetor.=--This condition may be
due to other causes than the vacuum system. Do not tinker with it until
you are sure that the trouble is not elsewhere. Flood the carburetor.
If gasoline runs out of the float chamber you may be sure that the
vacuum system is performing its work properly.
=To Remove Cover.=--To remove the cover for inspection, take out the
screws and run a knife blade carefully around the top to separate the
gasket without damaging it. Shellac the gasket before you replace it to
make the tank air-tight.
=Faulty Feed.=--If faulty feed is traced to the vacuum tank, one of
the following conditions may be the cause. The float valve G may have
developed a leak. To repair, remove the top of the tank to which it
is attached. Dip the float into a pan of hot water. Bubbles will
show the leak. Punch two small holes, one at the top, and one at the
bottom, and blow the gasoline out. Then solder up the holes and the
leak. Use solder carefully in order not to add too much weight to the
float. A small particle of dirt may be lodged under the flapper valve.
This trouble can usually be remedied by tapping the side of the tank.
In order to determine whether or not the flapper valve is working
properly, plug up the air vent tube and remove the pipe extending from
the bottom of the tank to the carburetor. Start the engine and place a
finger over the opening (from which you removed the tube). If continual
suction is felt, it is evident that the flapper valve is being held
off its seat. If tapping the side of the tank will not remedy this
condition, remove the cover and withdraw the upper chamber. The valve
is attached to the pipe projecting from the bottom.
=Strainer.=--Remove and clean the strainer screen located at V, Fig.
52, every five or six weeks. This screen collects all the dirt and
foreign matter in the gasoline, and often becomes stopped up.
[Illustration:
CONNECTION TO
GASOLINE TANK
SUCTION TUBE
CONNECTION TO INTAKE
MANIFOLD
STRAINER
VENT TUBE
CONNECTION
COVER
ATMOSPHERIC
VALVE
SUCTION VALVE
VALVE LEVER
INNER TANK
SPRINGS
OUTER TANK
FLOAT LEVER
FLOAT
GUIDE
FLAPPER VALVE
DRAIN PLUG
CONNECTION TO
CARBURETOR
Fig. 53. Vacuum System--Inside View of Parts--Stewart Warner]
=Filling the Vacuum Tank.=--To fill the tank after it has been cleaned
or repaired, leave the spark off, close the gas throttle, and crank the
engine over a few times with the starter or by hand. It takes less than
ten seconds to create sufficient vacuum to fill the tank.