Saab 95 1967, Service Manual

Page: 89 / 610

choke device with fast idling
The starting automatics feature a vacuum-regulated d'
phragm which, via a pull rod, opens the Strangler Valvla-
slightly as soon as the engine has started, thus providi:
sufficient engine air and preventing suffocation. To en_9
sure that this demand will be satisfied even when the vac.
uum falls in conjunction with acceleration, a device is
provided which on such occasions forces the strangler
valve to open.
The starting automatics include a ratchet device (ratchet
wheel With three steps) which serves to increase the idling
speed when starting from cold. The ratchet wheel is con-
trolled by the bimetal spring and the amount of increase
in idling speed is determined by the position adopted by
the ratchet wheel.
In order to engage the fast-idling device when starting
from cold, the accelerator pedal must be pressed right
down and then released before an attempt to start is
made. This is necessary in order to release the ratchet
Wheel, thus enabling the latter to take up the position de-
cided by the bimetal spring. The throttle valve is then ac-
tuated by the adjustable control rod and the idling func-
tion of the throttle valve is now moved from the idling
screw to the ratchet wheel.
Idling system
When the engine is idling, the throttle valve is almost
fUW closed (regulated by the idling screw) so that there
will be a large vacuum (negative pressure) around and
under it. The vacuum in the idling passage emanating
under the throttle valve will then be so great as to cause
fuel to be drawn up through the main jet and through a
special duct up to the idling jet. After having passed this
jet the fuel is partly mixed with the air admitted to the
idling system through its special air jet. The air jet is in
the form of a drilling and cannot be altered. The obtained
mixture of fuel and air is now drawn through the idling
duct via the air-regulating screw into the engine.
The said air-regulating screw is used to vary the through-
put area for the fuel, thus regulating the mixture of fuel
and air. As a certain amount of air is always passing the
throttle valve, the engine fuel-air mixture when idling
will be richer if the screw is screwed out and thinner if it
is screwed in.
IDLING SYSTEM
1. Idling air jet
2. Main jet
3. Idling duct
4. Air-regulating screw, idling mixture
5. Throttle valve
6. Adjusting screw. idling
7. Idlin9 fut" 1'“
SAAB 200—7