10. DISMANTLING AND SERVICING OF FUEL PUMP
The fuel pump and “permanent
magnet” motor (Fig. 26) can be dismantled and re-assembled without the use
of special tools.
A 110 volt A.C. mains connection will be
required for insulation tests on the pump motor armature; and a lathe for
skimming the armature should this be necessary.
Note: It is essential that the working area
on the bench is clean (free of dirt, metal and swarf etc.) otherwise it will
be attracted inside the yoke by the exposed field magnets. A piece of clean
rag pushed into the yoke will help to keep out any dirt etc.
When re-assembling the yoke to the
armature do not allow it to snap hard against the ceramic magnets and damage
(i) Remove the six bolts which secure the
pump unit to the pump housing and withdraw pump unit. (The pump unit
components are not serviced individually. Fit a complete new unit if original
(ii) Remove and
discard the ‘0’ ring situated in the end of the pump housing.
(iii) Remove the two through bolts which
secure the yoke to the housing. Grip the exposed tongue of the armature shaft
with a pair of pliers and gently remove the armature and housing assembly from
(iv) Hold the housing in a vertical position
(armature uppermost) and gently withdraw armature from housing.
Note: At this stage the assembly must be held in a vertical
position to ensure that the shimming washer(s) on the armature shaft slide off
as the armature is withdrawn. Otherwise, they will stick to the armature and
damage the brushes as the armature is withdrawn.
Fit new brush plate assembly if brushes are worn
to less than 0.125” (3.17 mm) in length.
Use an armature tester to check armature for open or short-circuited
windings. Check armature insulation using a 15W 110 volt A.C. mains test
lamp connected between each commutator bar and armature shaft. Armature
resistance between adjacent commutator bars should be within the limits 0.16
to 0.24 ohms at 150C.
The commutator should be cleaned using a petrol moistened cloth, and
light scratches removed by polishing with a very fine glass paper. A badly
scratched or worn commutator should be skimmed on a high-speed lathe. Do not
remove more metal than is necessary. DO NOT UNDERCUT THE INSULATORS BETWEEN THE ARMATURE SEGMENTS
(iv) Pump Unit
Visually examine for signs of wear etc. The pump unit must be renewed,
if worn, as component parts are not serviced individually.
Visually examine for signs of wear etc., and
renew if necessary.
(c) Pump Motor Rubber Seal
Evidence of petrol discharge from the small drain pipe on the body casting indicates
failure of the rubber seal
(between the pump and motor) through which the drive
shaft passes. In such cases fit a new seal. To check the seal proceed as
(i) Connect the pump inlet to a
(ii) Connect a pipe to the pump
outlet union, and immerse the free end in kerosene.
(iii) Connect the motor cables to a 12 volt D.C. supply.
(iv) When the pump is running and
held well above the kerosene supply a continuous flow of bubbles discharged
from the outlet pipe indicates that the seal is faulty.
(d) Re-assembly of Pump and Motor
Re-assembly of the pump and motor is the
reverse of the assembly procedure. Great care must be taken to avoid damaging
the thicker petrol seal (see 12 in figure 26) when passing the armature
shaft drive tongue through the base casting.
The seal should be smeared with grease (Shell 6266) before assembling and a
temporary protective cover fitted over the end of the armature shaft. (Figure
27 gives the dimensions for making a suitable cover. Alternatively, the
bullet-shaped cap from a ball-point pen can be used as a protective cover).
Ensure the assembly marks (see 13 in Figure
26) on the motor yoke and body casting are in line when assembling them
together, otherwise reverse rotation will result.
Bolt pump and motor together after checking
that the drive assembly is satisfactory, and correctly located.
(e) Armature End-Float Adjustment
After assembling pump and motor, hold the
pump unit with the yoke vertical (end-float adjustment screw uppermost) and
proceed as follows:
(I) Slacken the locknut for end-float
adjustment screw and screw in adjuster until resistance is just felt. Screw
the adjuster back a 1/4 of a turn to give the
correct end-float within the limits 0.004” to 0.010” (0.10 mm to
0.25 mm). Lock the screw in position.