Austin SEVEN - The Petrol Pump; How Fuel is supplied from the Tank to the Carburetter; How it works

THE PETROL PUMP.
How Fuel is supplied from the Tank to
the Carburetter
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ETROL is drawn from the tank at the rear'by means 01 an A.C.
petrol pump which advances the Inel in the correct quantity demanded .
by the carburetter, no more and no less.
Service on the petrol pump is available at all Austin Dealers and at all
A.C. service stations, which are prepared with parts and lixtures lor
repairing and adjusting all pumps il any trouble is experienced with the
Inel supply.
Make sure that any dilliculty is not due to causes apart Irom the
pump belore attempting to do anything to the pump.
11there appears to be lack ollnel at the carburetter. lirst ascertain
if there is any Inel in the tank, and il not. replenish. Make sure that the
pipe and connections between the tank and the pump, and between ,the
pump and the carhuretter, are not leaking. In case 01 broken or damaged
piping replacement should be made.
lt may be that the litter cover of the petrol pump is loose. 11this is
the case, tighten the main nut at the top, lirst ascertaining that the cork
gasket lies lIat in its seat and is not broken or unduly compressed. A
gasket compressed hard may need to be replaced.
Clean the Filter.
Occasionally remove the cover and dean the lilter screen underneath it.
Also remove any sediment Irom the chamher below the lilt er by taking out
the drain plug (F.) Make sure that the libre washer is under the head 01th.
plug belore replacing.
When re-assembling, take care that the cork gasket is replaced correctly,
under the cover, and that the libre washer is under the head 01the screw.
11petrol appears to be leaking at the edge 01 the diaphragm tighten
the cover screws alternately and securely, but do not attempt to dismantle
the pump body.
Sometimes there appears to be a leakage 01 luel at the diaphragm
joint. The leakage may actually exist at one 01 the pipe littings, causi~g
the Inel to run down the pump on to the diaphragm lIange.
In hot weather when petrol is likely to evaporate, or when dilliculty
might be expected on cold mornings, it is advisable to lilI the carburetter
by operating the hand priming lever on the pump before attempting to
start the engine. lt will be appreciated that il the engine comes to rest
when the rocker arm is on the high point 01 the eccentric the priming lever
will be inoperative. In the event 01 this the engine should be turned
over one revolution by hand.
The pumping action 01 the diaphragm can be distinctly lelt until
the carburetter bowl is lull.
Alter removal 01the upper casting on any type 01A.C. Inel pump it is
important that the cover should only be replaced while the pump pull rod
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is at the top 01its stroke. This is to ensure sullicient lIexing01the dia.
phragm to allow its normal working movement.
How it works.
By revolvingshalt (P) the eccentric(0) willjilt rockerarm (Q) which
is pivoted at (S) and which pulls the pull rod (K), together with the
diaphragm(H), downwardagainstthe spring pressure U), thus creatinga
vacuumin the pump chamber (C).
Fuellrom the rear tank willenter at (D) into sediment chamber(E)
and through the lilter gauze(A)and suctionvalve(M) into pumpchamber
E
F
G
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H
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K
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The A.C. Fuel Pump.
F-D"'n PI",.
L-Prim'n, lm..
(C). On the return stroke spring pressure U)pushes the diaphragm (H)
upward, lorcing the luel Irom chamber (C) through pressure valve (C)
and opening (B) into the carburetter.
When the carburetter bowl is lilled the lloat in the lloat chamber will
shut 011the inlet needle valve, thus creating a pressure in pump chamber
(G). This pressure will hold diaphragm (H) downward against the spring
pressure U)and it willremainin this positionuntil the carburetterrequires
lurther Inel and the needle valve opens.
The rocker arm (Q) is in two pieces, the outer one operating the inner
by making contact at (R) and the movement 01the eccentric (0) is absorbed
by the "break" when Inel is not required.
Spring (N) is merely lor the purpose 01 keeping the rocker arm (Q)
in constant contact with the eccentric (0) to eliminate noise.
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