Triumph TR6 PI Operation Manual page 152

FUEL SYSTEM - PI
Control Unit
The control unit is attached to the metering
unit by four bolts. A cam follower with a diaphragm
seal set in an annular groove around its periphery
projects through the leading face of the unit. The rear
end of the cam follower bears against the outer two
of three rollers carried on the control links, whilst the
third roller of smaller diameter runs against the fuel
cam or datum track.
The control links are pivoted at the top where
they are attached to the centre of a spring controlled
rubber diaphragm - the lower part of the control
links are free.
Two springs are positioned between the
diaphragm and three concentric calibration screws.
The top of the diaphragm and the calibration screws
are in a chamber connected by a pipe to the
manifold.
The fuel cam or datum track is secured by two
screws to a carrier which is in contact with an
external control screw. The carrier is pivoted at point
X and the pivot extends through the rear face of the
unit. The excess fuel lever is pivoted at the rear face
of the unit and has a cam face at the lower end which
contacts the cam carrier pivot.
Engine fuel demands, according to throttle
openings and load, are reflected in changes in inlet
manifold depression. The change is sensed by the
spring loaded diaphragm which takes up a position
balancing the loading of the springs against the
depression in the chamber. The central links are thus
raised or lowered along the cam track allowing the
follower in or out of the forward face of the unit and
so regulate the metering unit variable stop. To
prevent the full hydraulic force of the variable stop
from impinging on the control linkage a balancing
spring
is
fitted on the cam follower which results in
only light pressure between the follower and the
rollers. Movement of the excess fuel lever for cold
starting is effected by pulling the choke control knob
on the control panel. This alters the position of the
excess fuel lever and the carrier for the cam is drawn
away from the cam follower thus causing the shuttle
to travel further. When the control knob is pushed
back the carrier is returned to the normal operating
position by the action of a tension spring.
CAUTION:
It is important that under no circumstances
must the follOWing adjustments be altered:-
a) Calibration screws
b) Full load setting screw
d) Datum track screws
19.35.00 P.1. Sheet 4
I\ITOU.•
8 2
I. Cam follower
2. Rollers
3. Control links
4. Fuel cam (datum tank)
5. Calibration springs
6. Calibration screws
7.
Fuel cam carrier
8. Full load setting screw
9.
PointX
10. Excess fuel lever
11. Balance spring
12. Depression chamber
13. To manifold
14. To atmosphere
Triumph TIl6
MaDuaJ. Put
No. 54'%77 . . .
1