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3-20
FUEL AND VACUUM PUMP
ENGINE FUEL
AND EXHAUST SYSTEMS
(94)
1. Make certain that there is gasoline in the
tank.
2. With engine running, inspect for leaks at
all gasoline feed pipe connections at gasoline
tank, fuel pump, gasoline filter, and carburetor.
Tighten any loose
connections.
Inspect the flex-
ible connection in feed line and all pipes for
dents or kinks which would restrict the flow of
fuel. Air leaks or restrictions on
suction
side
of fuel pump will seriously affect pump output.
3. Inspect for leaks at fuel pump diaphragm
flange. Tighten the cover screws alternately
and securely. Do not use shellac or any other
adhesive on diaphragm.
4. Clean the filter in fuel pump and gasoline
filter at carburetor (par. 3-9) and make sure
that filter bowl gaskets are sealing securely.
5. Disconnect pump-to-carburetor pipe.
Ground primary terminal of distributor with
jumper wire so that engine can be cranked
without firing. Place suitable container at end
of pipe and crank engine a few
revolutions.
If
no
gasoline,
or only a little, flows from pipe
the feed pipes are clogged or fuel pump is in-
operative. Before condemning the fuel
pump,
disconnect feed pipes at pump and blow through
them with air hose to make sure that pipes are
clear.
6. If gasoline flows in good volume from
pipe at carburetor it may be assumed that the
fuel pump and feed pipes are okay;
however,
it is advisable to make the following "static
pressure" test to make certain that fuel pump
is operating within specified pressure limits.
7. Attach a suitable pressure gauge to the
disconnected end of gasoline pipe at carburetor.
Run engine at 450 and 1000 rpm on gasoline in
carburetor bowl and note reading on pressure
gauge.
8.
If
fuel
PUI}1P
is operating properly the
pressure will be 4 to 5 pounds and will remain
constant at speeds between 450 and 1000
rpm.
If
pressure
is'
too low or too high, or varies
materially at different speeds, the pump sho
uld
be removed for repairs (par. 3-19).
NOTE:
If
pressure
gaug
e
is connec ted at pump outlet
instead
of at end of f
eed pipe
th
e pressu re
should be 41;2 to 51;2
pounds.
3-
18
VACUUM
PUMP
INSPECTION AND
TE ST
To test the vacuum section of pump, fully
open the windshield wiper valve and observe
the wiper blade while alternately idling and
accelerating
the engine. Operation of the wind-
shield
wiper should continue at nearly constant
speed
regardless of the engine speed or throttle
opening. NOTE: A dry windshield has the effect
of slowing wiper blades in comparison with
operation
over
a wet windshield. Consider this
when testing, or wet the windshield by spraying
with water.
If
windshield wiper does not oper-
ate properly make the following inspection and
test.
1. Check windshield wiper transmission
cables to make sure they are correctly attached
to wiper motor, are properly located in pulleys
on wiper transmissions and cable tensioners,
and are not rubbing against anything under
the cowl. Make certain that wiper control is
connected so that it can fully open the motor
valve.
2. Check tightness of vacuum pump cover
plate screw and check all pipe and hose con-
nections between pump and windshield wiper
motor. Tighten
loose
connections and replace
any cracked or deteriorated hose.
3. If windshield wiper does not operate
properly after all points of leakage have been
corrected, detach both pipes at vacuum pump
and join them with a
piece
of rubber hose.
Slowly operate engine from idle to about 25
MPH speed; the wiper should run at full speed
operating on engine vacuum only. If it does
not, it can be assumed that the wiper motor,
or tubing is
defective.
The pump vacuum sec-
tion is inoperative if the windshield
wiper
oper-
ates properly on engine vacuum but not on
pump vacuum.
4.
A further test of vacuum pump may
be
made
by attaching a vacuum gauge to the inlet
port (port connected to wiper motor), with
outlet pipe disconnected. CAUTION:
Always
make this
test
of vacuum pump with the outlet
open. The downward or exhaust stroke of pump
is positive and the m
echanism
may be damaged
if the outlet is closed or restricted.
5. With engine operating at equivalent of 20
MPH road sp
eed,
the gauge should show 7 to 12
inches of vacuum. Less than 7 inches of vaccum
indicates an inoper ati ve va
cuum
pump.
6. Before removing the fuel and vacuum
pump
assembly for repairs to vacuum section,
it is advisable to remove the cover plate and
check condition of cover plate and screw gas-
kets, and condition of the screen under the
cover plate. Leaking
gaskets
or a plugged screen
would affect vacuum pump operation.
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