Engine Control Components; Ignition Solenoid; Fuel Pressure Solenoid; Throttle Jack Solenoid - Lotus TURBO ESPRIT Service Manual

Page
2
SECTION EMA
EM4.
1
.
-
ENGINE
CONTROL COMPONENTS
Ignition Solenoid
Located beneath front of plenum chamber. Function i s to advance ignition on operation
o f choke.
A
micro-switch operated by the dashboard end o f the choke cable (which also
operates the choke t e l l tale lamp) energises the ignition solenoid. The signal to the
distributor vacuum advance capsule (normally connected to N o .
1
cylinder throttle
edge drilling) i s then switched to the vacuum pump, and thus f u l l ignition advance i s
achieved, together with an increase i n engine idle speed.
Fuel Pressure Solenoid
Located beneath rear of plenum chamber. Function i s to reduce fuel pressure on 'overun'
and idle.
A
micro-switch, mounted on the front of the front carburettor, and cperated by
the throttle lever i n i t s fully closed position, energises the fuel pressure solenoid. The
signal to the fuel pressure regulator (normally connected to boost pressure i n the plenum
chamber) i s then switched to No.
1
cylinder inlet manifold depression, thus reducing
0
-
fuel pressure to the carburettors and mixture strength under closed throttle 'overun'
conditions.
Throttle Jack Solenoid
Located on the front o f the front carburettor. Function i s to increase engine idle speed
when engine
i s
cold or air conditioning switched on, and also to open throttle on hot
start cranking mode.
A
thermostatic switch fitted into the rear o f the i n l e t manifold
0
water rail, makes contact at water temperature below
70
C, and energises the throttle
jack solenoid. To aid cold starting the solenoid i s de-energised whilst i n the cranking
mode,
A t
water temperature above
70°c,
the solenoid i s energised O N L Y whilst
cranking to a i d hot starting. The solenoid
i s
alsoenergised when the ACU i s switched on.
Air
Pump
&
Divertor Valve
d he
a i r pump i s mounted on the rear of the engine and driven by
'v'
b e l t from
the
exhaust
0
cdmshaft. The divertor valve i s fitted on the outside of the ehgine bay left hand wall.
Their function i s to provide additional air into eitherthe exhaust ports, or the exhaust
catalyst, and reduce engine emissions.
The a i r pump draws a i r from a filter located on the right hand rear wheel arch and supplies
it to the divertor valve.
The divertor valve i s spring loaded so as to supply a i r to the
exhaust ports via a non-return valve, and air injection manifold.
0
When engine coolant temperature reaches.70 C, a solenoid on the divertor valve i s
energised,
and
connects a diaphragm chamber on the valve with vacuum supplied by
the engine driven pump.
This
vacuum is used to overcome spring pressure and divert
a i r flow via a non return valve to the exhaust catalyst.
APR 1987