Perkins L4 - Page 60

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Page S8
Fue/ Injection System-continued
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FIG. SS. Removing diaphragm from pneumatic govemor.
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(e) Tbe control rod should then slowly return
to the maximum speed position af ter a
quick initial movement for a fraction of
the distance. Ir it returns quickly for the
whole movement and the housings are
clamped firmly together, then the diaphragm
is leaking and should be replaced by an
authorised agent. Instructions for replace-
ment are given below.
If the diaphragm appears to be sound as indi-
cated by this test, suspect the vacuum pipe and
test in a similar way. Replace the union of this
pipe on the governor casing and uncouple it at
the butterfly end. Repeat the test as before but
placing the finger on the uncovered end of the
vacuum pipe.
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For preference, use a picce of sheet metal about
tin. (19.0 mm.) wide, shaped at tbc end to fit
the curve of the rim, and sharpened to an edge
similar to that of a screwdriver.
Lift the edgc of tbc rim carefully at! round.
When tbc rim is frec, slide tbc socket at tbe
back of tbc diaphragm off tbc pin in tbc control
rod.
Be careful not to mark tbc face of tbc fuel
pump on to which the governor casing fits.
To rcplace tbc diaphragm first place the socket
on tbc pin in tbc control rod.
Then prcss the rim tirmJy in its place.
Replacc the governor casing. being careful to
screw the setscrews very tightly and evenly in
position.
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CAunON.
Tbe pneumatic governor dep:.nds tor its action
upon pressure variations set up in the air intake
pipe of the engine by the venturi con trol valve.
If this should be removed either by itself or with
the inlet manifold during overhaul or it the vaCUUJT,
pipe unions are not always kept perrectly tight.
then the governor may rail to operate causing
damage to the engine.
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To Renew Leather Diaphragm.
To renew the Ieather diaphragm proceed as
follows :
Disconnect the vacuum pipe.
Take out the screws holding the pneuma tic
governor in place.
Tbe diaphragm will then he accessible. lt is
held in a light U-section meml riJn which must be
prised from the cas ing. Sec Fig. S.5.
Great care must be exercised in this operation.
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