INTRODUCTION
This Workshop Manual
Supplement is complete in itself and deals with the Workshop procedure
appertaining to remove, refit, overhaul and adjust the Automatic enrichment
device (A.E.D) fitted to the Rover V8 engine.
Description of Automatic enrichment device
(A.E.D)
The Automatic enrichment device is a fully automatic auxiliary carburetter
for providing an internal combustion petrol engine with the necessary
fuel/air mixture in excess of that supplied by the standard carburetters
whilst the engine is below its normal working temperatures.
It consists of a small carburetter complete with float chamber and a throttle
in the form of a valve opened or closed by the deflection of a temperature
sensitive bi-metallic strip.
Referring to the diagram the main valve (10) and its seating (13) form
the orifice controlling the volume of fuel/air mixture admitted to the
engine.
The main valve is connected to the main bi-metal (22) by spindle (6) which
slides freely in the low friction carbon bush (8). By this means the valve
orifice is determined by the temperature of the main bi-metal (22), the
lower the temperature the larger the orifice.
The outlet pipe (32) is connected to the inlet manifold and the inlet
pipe (28) is connected to a hot air pick-up on the exhaust manifold so
that filtered air drawn through the device via the carburetter elbow is
heated as the engine warms up.
The main bi-metal (22) is attached to the heat shroud (20) which serves
as a heat storage and also as an adjustable member for the main valve,
being loaded down by spring (21) into grooves (23) formed in the valve
body (11) and abutting against the adjusting screw (1).
The main valve (10) is prevented from being drawn down by manifold depression
on to its seating by the diaphragm (25) which is subjected to the depression
in the balance chamber (24). This depression is provided by the matching
of the two orifices (33) in the main valve and the orifice (9) in the
valve body.
The fuel orifice (18)is situated at the lower end of the jet tube (14)
surrounding which is the fuel well (16). This is filled with fuel whilst
the device is out of action via the fuel orifice (18) and the well orifice
(17) in the side of the jet tube, and is discharged via the well orifice
immediately after the engine is started from cold.
The needle diaphragm (30) in conjunction with the diaphragm spring (31)
raises or lowers the tapered fuel needle (15) in response to changes in
manifold depression, the lower position of the needle, or normal idling
position being established when the circlip (4) rests on the upper face
of the adjusting nut (5) under the influence of spring (7) and the upper
position of the needle is determined by the needle coming to rest against
the secondary bi-metal (3) so that at low temperatures the needle is withdrawn
further out of the fuel orifice.
Fuel enters the float chamber (34) via fuel pipe (35) and the fine mesh
nylon filter (36) to the viton tipped and spring loaded float needle (37)
which in conjunction with the float (38) controls the level of fuel in
the float chamber.
A drilled passage (39) feeds fuel to the fuel orifice.
