(v) Fit a flat washer and secure the
assembly with a circlip.
(vi) Fit the pivot shaft/datum track spring.
(vii) Assemble the rollers to the control
links - small roller in the middle, large rollers
with chamfered edge facing
inwards. This should be done by first fitting the roller
pivot to one of the
links and securing with a circlip. The rollers can be located in position
rotating the link so that the pivot pin is uppermost.
(viii) Next, place the spherical bearing
in position at the end of the link.
(ix) Fit the remaining link arm and secure
(x) Replace the backing plate, diaphragm,
diaphragm support and spring seat in that order.
(xi) Screw on the diaphragm locking nut
and tighten to 4 lbf (17.80 N).
(xii) Lightly smear link rollers with a little Rocol MD-0.
(xiii) Re-fit link arm and diaphragm
making sure that spherical seat and link arm are
square with the rest of the
(xiv) Push diaphragm rim into its seating on the body.
(xv) Assemble calibration springs - large
spring on the diaphragm, then spring carrier
and small spring.
(xvi) Fit depression chamber cover and
overfuel lever bracket. The bracket should be
positioned so that its cranked
end is nearest the drive end of the metering distributor.
The air inlet
connection must be positioned on the opposite side to the banjo connections.
Note that the two longest fixing screws are used on the bracket side of the
(xvii) Position the cam follower diaphragm
with the three locating slots uppermost, feed
cam follower through hole in
diaphragm. (The diaphragm can be pushed on to its seating
on the cam
follower by finger pressure).
OF METERING DISTRIBUTOR TO CONTROL UNIT
(i) Fit spring thrust plate over cam
(ii) Position cam follower and spring
between the control unit and metering distributor and
secure one to the
other. Ensure that the diaphragm seal is seated correctly.
5. SETTING THE
DATUM TRACK ANGLE
After re-assembling the metering unit, some
mechanical settings or adjustments must be made
before the unit is tested on
the test bench.
Note: These initial adjustments ensure
that the angle of the datum track is correct.
Otherwise, there will be
reduced performance at engine idling speed and at light load
When setting the metering unit, adjust the maximum fuel screw and the
track to obtain the required gap between rollers and cam follower.
The complete calibration procedure is
necessary if the calibrating screws have been moved
from their original
(a) Test Equipment
(i) A fully equipped fuel injection test
(ii) A set of flat feeler gauges.
(iii) A tool to assist in the setting
operation. (A 16AC end bracket fixing bolt can be
used, provided it is
threaded along its entire length. Alternatively, a 5/16“ UNF bolt,
3k” (89 mm) long, with two locknuts can be used, see Fig. 23.
(iv) A collar 0.540” (13.72 mm) thick to
fit over the bolt. See Fig. 23.
(v) A datum track locking tool (see Fig.
(b) Setting Procedure
The procedure concerns adjusting the control
unit datum track to the correct angle,
and also the amount of roller travel.
With the metering unit bolted to the test bench
the sequence is as follows:
(i) Remove plastic covers from the
depression chamber and datum track housing.
Note: Replace the depression chamber
cover fixing screws.
(ii) Remove minimum fuel stop screw and
locknut, see Fig. 23.
(iii) Insert locking tool and check that
clearance between the roller and the cam follower
(see Fig. 22, position 1),
is 0.058” (1.47 mm).
(iv) If incorrect, remove locking tool and
adjust datum track by means of the maximum
fuel screw until 0.058” (1.47
mm) clearance is obtained. Repeat (iii) with locking tool in
(v) Insert 5/16“ UNF bolt complete with
locknuts in place of minimum fuel stop screw.
Screw bolt until it just
bottoms on the spherical bearing stop pin, see Fig. 23.
(vi) Screw locknuts against inner spring
stop and lock together on the bolt.
(vii) Unscrew bolt with both nuts locked
together, until 0.540” (13.72 mm) collar
just fits between locked nuts and
inner spring stop, see Fig. 23.
(viii) Apply vacuum to depression chamber.
(17” Hg for TR5 unit and 24” Hg for TR6
and 2.5 ‘P.I.’ units).
(ix) Place a flat feeler gauge between roller and cam follower. 0.012”
(0.30 mm) for
TR5 unit and 0.002” (0.050 mm) for TR6 and 2.5 ‘P.I.’ units.) See Fig. 22,
(x) Loosen the two datum track securing screws and adjust datum track
clearance is obtained. Re-tighten securing screws and check clearance.
(xi) Return depression chamber to atmospheric pressure and re-check
clearance at position 1 (see Fig. 22) re-adjusting if
necessary. Re-fit the minimum fuel stop
screw and locknut.