Page 129 - Vauxhall 20-60 H.P. (R Type) Chassis Shop Manual

VAUXHALL 20-60 SHOP MANUAL

PETROL PUMP ( After R4236 )
( See Figure 36 )

SECTION Description: — On and after car bearing chassis number R 4237 the Autovac
567 has been replaced by a petrol pump which is located on the near side of the

engine crankcase and is driven by an eccentric machined on the camshaft.
As the camshaft rotates, the rocker arm, which is pivoted at the centre, lifts
and pulls the diaphragm linkage, together with diaphragm held between
metal discs, downward against the pressure of the diaphragm spring, thus
creating a vacuum in the pump chamber.
Petrol from the main tank then passes into the glass bowl through the two
gauze filter screens and suction valve into the pump chamber. On the return
stroke the pressure of the diaphragm spring pushes the diaphragm upwards,
forcing the petrol from the pump chamber through the non-return valve
to the carburettor. When the carburettor float chamber is filled, the float
forces the needle valve on to its seating, thus preventing any more petrol
passing into the chamber. This creates a pressure in the pump chamber,
which forces the diaphragm down, where it will remain until a further
supply of petrol is required by the carburettor. The rocker spring keeps the
rocker arm in constant contact with the eccentric on the camshaft.

TO REMOVE

SECTION – Disconnect petrol pipes from pump body. Remove the nuts from the
568 studs holding the pump to the crankcase and the pump complete with
filter can be withdrawn.

INSPECTION

SECTION – Examine and clean glass bowl and filter screens ( Section 572 ) .
569 The pump is sealed by the Manufacturers and should not be interfered

with. If the pump will not function, it should be replaced by a new one
( Section 571 ).

TO REPLACE

SECTION Reverse operations given for removal ( Section 568 ) .
570 A paper joint is fitted between the face of the pump body and the crankcase,

if this joint is damaged, it is essential that it is replaced by one of equal
thickness otherwise the operation of the pump will be affected.

When replacing the pump great care must be taken to see that the rocker
arm is on top of the cam, and not under it, otherwise it will be broken in the
first revolution of the camshaft.

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