FUEL SYSTEM - N.9
a higher speed than specified or severe damage
to the engine may be the result.
Idling Speed Setting
The engine idling speed is adjusted by the idling
screw (see Fig. N.13).
With the engine warm, turn the screw clockwise to
increase the engine speed and anti-clockwise to
decrease.
The idling speed may vary, depending upon the type
of craft to which the engine Is fitted. For details apply to
the nearest Perkins Distributor, or alternatively, Service
Dept., Perkins Engines Limited, Peterborough.
ATOMISERS
General
Each atomiser body consists of a steel body held to
the cylinder head by means of a flange and two studs.
The joint between the atomiser and cylinder head is
made by a copper washer between the lower face of the
nozzle cap and the cylinder head.
When preparing to fit the atomiser into place in the
cylinder head, care should be taken, that only the correct
copper washer is used to make this joint. The metal of
the cylinder head, the faces of the copper joint ring, and
the corresponding face on the nozzle holder cap nut
should be perfectly clean if a leak-proof joint is to result.
It is advisable to fit a new joint washer when the
atomiser is replaced after having been removed for any
reason.
Ensure that the old washer has been removed from
atomiser or cylinder head.
This joint washer should be an easy, but not loose fit
for the atomiser nozzle, and it is because this is such an
important feature that the washers especially made for
the purpose should be used and none other. On no
account should ordinary sparking plug type washers be
used.
The atomiser can now be fitted in place, care being
taken to see that it is an easy fit in the cylinder head and
on the holding-down studs, so that it can be placed down
on the copper joint without force of any kind. The nuts
on the flange should then be tightened down evenly in
order to prevent the atomiser nozzle being canted and
so "nipped" in the cylinder head.
The correct tightening torque for the atomiser
securing nuts is 12 lbf ft (1,7 kgf m) - 16 Nm.
When fitting the leak-off pipes make sure new
washers are used, and before tightening the banjo bolt
make sure the washers are a good fit and are placed
centrally, and remain central when tightening the bolt.
MAINTENANCE
The following information is given for the guidance of
those who wish to carry out their own atomiser
maintenance using the basic test equipment, which
would include an Atomiser Testing Pump and kit of tools.
(Refer Figs. N.14 and N.17).
Atomisers should be taken out for examination at
regular intervals. How long this interval should be is
difficult to advise, because of the widely different
conditions under which engines operate. When
combustion conditions in the engine are good and the
fuel tank and filtering system are maintained in first-class
order, it is often sufficient if the atomisers are tested
every 2,500 hours.
It is no use taking atomisers out of attention unless
the equipment described above is available, or spare
atomisers are at hand for substitution.
The nearer the ideal conditions of good fitting with
adequate cooling and absolutely clean fuel are realized,
the less attention the atomisers will need, and so the
longer their efficient life. In this connection, since there
is no other item of the equipment upon which the
performance of an engine depends so much, it pays the
user handsomely to see that the engine never runs with
any of its atomisers out of order.
Fig. N.14.
Complete Kit of Tools for use when cleaning and
overhauling atomisers.
