WSM.124
Section C (Fuel System)
the suction pipe clear of the paraffin (kerosene.)
Again operate pump. Not more than 16 strokes
should be necessary to secure delivery of paraffin
from the pump outlet.
With the same apparatus a second test can be made
by working the pump with the tap on the delivery
side closed, pressure then being recorded on the
gauge. After ceasing to work the pump it should
take several seconds for this pressure to return to
zero, thus denoting that the valves are seating
properly. Also, while there is pressure, the outer
edge of the diaphragm-visible between the two
clamping flanges-should be carefully examined for
leakage and the retaining screws tightened if
necessary. When working the pump by hand a
somewhat longer stroke is obtained and the
pressure developed is apt to be higher than when
fitted to the engine.
When the above apparatus is not available the
pumps should be tested, using a pan of clean
paraffin as follows:-
Flush the pump by immersing it in the paraffin
and working the rocker arm half a dozen times,
then empty the pump by continuing to operate
it while held above the bath. Then with the
pump clear of the paraffin bath, place the finger
over the inlet union (marked "in") and work
the rocker arm several times. Upon removing
the finger a distinct suction noise should be
heard, denoting that the pump has developed
a reasonable degree of suction. Afterwards the
finger should be placed over the outlet union
and after pressing the rocker arm inwards the
air drawn into the pump chamber should be
held under compression for two or three
seconds; this· should be done with the pump
immersed in paraffin and the clamping flanges
of the diaphragm watched for any signs of air
leakage.
TO REFIT PUMP TO ENGINE
Reverse the procedure outlined for removal from
engine. Ensure that the rocker arm is correctly
positioned. After refitting the pump, the engine
should be run for a short time and pipe unions and
pump examined for any signs of fuel leakage.
I
st re-issue
Page 7
EXCESSIVE FUEL PUMP PRESSURE
As explained under, "Details of Operation"
the pressure of fuel on the carburettor is determined
by the spring (12, Fig. 1), and the further this spring
is compressed the greater will be the pressure. All
parts of the pump and the cylinder block are
machined to definite limits, and if all the lower
limits exist on one particular engine, the spring will
be compressed on the downward stroke to a greater
extent than is normal, resulting in an excess
pressure at the carburettor.
Excessive fuel pump pressure can be a cause of
heavy fuel consumption. This can be checked and
if necessary rectified as follows:-
1. Disconnect the pipe to the carburettor at the
pump.
2. A mercury manometer or a suitable reliable
pressure gauge calibrated up to 6 lb. per sq. in.
(0·422 kg. per sq. cm.) should then be connected
to and as near as possible, on the same level
with the outlet on the pump.
3. Rotate the engine on the starter, and a reading
similar to that given in the Data Section under
"Fuel System" should be recorded on the gauge.
To remedy excessive output pressure additional
packings should be fitted between the fuel pump
flange and cylinder block pump mounting face.
Excessive output pressure can be caused by
stiffening up of the pump diaphragm, and diaphragm
condition should be checked on any pump that has
been in service for a long time.
Care shou Id be taken to avoid the use of an excessive
number of packings as this can cause fuel starvation
under full throttle conditions.
The pump output pressure should always be
rechecked after adding packings.
Important Note
It must be clearly understood that the actual
mounting on the engine affects the output pressure
of the pump and thus these tests cannot be carried
out unless the pump is mounted in its normal
position. The use of jigs or other fixtures for
testing A.C. pumps will not necessarily give the
same results.
Summary of Contents for ALPINE I SERIES: APLINE II SERIES
Page 1: ......
Page 189: ...Fis 21 Ball pin heirht checkinr fixture in position Details of items 1 to 4 In Fig 22...
Page 208: ...Fla 3 Exploded view of rear axle Hypoid Bevel Drive...
Page 220: ...Page 16 WSM 12 f Section G Rear Axle 0 QQ I I I I I t 0 ii 8 ts t 0 Cl 2 i J...
Page 247: ...Page6 WSM 124 Section J Steering N Iii it...
Page 299: ...Page 40 3 6 7 8 Fis 22 Se rvo unit exploded view Sect WSM 124 ion K Brakes 18 419 GZo 21...
Page 413: ..._ PRINTED IN ENGLAND 9Y WREN PRINTING CQ LTD LONDON...