Chevrolet Light Duty Truck 1973 Service Manual page 462

6 M - 3 8 ENGINE FUEL
T O R Q U E A T 2 0 LBS. IN
I NOTE I Polyurethane Band must wrap
over both end seals of paper element as
shown.
POLYW RApZjL^^.
AIR C LE AN ER ELEMENT
B A N D S H O W N ) .
PAPER FILTER P O R T IO N
O F P O L Y W R A P AIR
C LE A N E R ELEM ENT
Fig. 9A—Installing the Polyurethane Band
THERMOSTATICALLY CONTROLLED AIR
CLEANER
This system (fig. 10A and 11 A) is designed to improve
carburetor operation and engine warm-up characteristics.
It achieves this by keeping the air entering the
carburetor at a temperature of at least 100 degrees F or
more.
The thermostatic air cleaner system includes a
temperature sensor, a vacuum motor, and control
damper assembly mounted in the air cleaner, vacuum
control hoses, manifold heat stove and connecting pipes.
The vacuum motor is controlled by the temperature
sensor. The vacuum motor operated the air control
damper assembly to regulate the flow of hot air and
underhood air to carburetor. The hot air is obtained
from the heat stove on the exhaust manifold.
Inspecti on-Visual
1. Check for proper and secure connections of heat
pipe and hoses.
2. Check for kinked or deteriorated hoses. Repair or
replace as required.
Operational
1. Remove air cleaner cover and install temperature
gauge (Tool J-22973) as close as possible to sensor
( % 12 A).
Reinstall cover without wing nut. (Temperature must be
below 85 degrees F before proceeding).
2. With the engine "O FF", observe damper door
W IN G J s lU T
completely cover the outer screen
surface of paper element as shown.
position through snorkel opening. Snorkel passage
should be open. Fig. 11 A, View A. If not, check for
binds in linkage.
3. Start and idle engine. W ith air temperature below
85 degrees F, snorkel passage should be closed. Fig.
11 A,View B. When dam per door begins to open
snorkel passage, remove air cleaner cover and
observe thermometer reading. It should be between
85 degrees F and 115 degrees F.
4. If damper door does not close completely or does
not open at correct temperature, continue with the
following vacuum motor check:
a. Turn off engine. Disconnect diaphragm assem­
bly vacuum hose at sensor unit.
b. Apply at least 9 in. Hg. of vacuum to diaphragm
assembly through the hose. This can be done by
mouth. Damper door should completely close
snorkel passage when vacuum is applied. If not
check to see if linkage is hooked up coorectly
and for a vacuum lean.
c. With vacuum applied, bend or clamp hose to
trap vacuum in diaphragm assembly (fig. 13A).
Damper door should remain in position (closed
snorkel passage). If it does not, there is a vacuum
leak in daiphragm assembly. Replace diaphragm
assembly.
5. If vacuum motor check is found satisfactory,
replace sensor unit.
VACUUM MOTOR REPLACEMENT
Removal
1. Remove air cleaner from engine.
2. Drill out spot welds fastening vacuum motor
retaining strap to snorkel tube.
3. Remove vacuum motor by lifting and unhooking
linkage rod from damper door.
Replacement
1. Drill 7/64" hole in snorkel tube at center of
vacuum motor retaining strap (fig. 14A).
2. Connect vacuum motor linkage to dam per door.
Fasten retaining strap to air cleaner with sheet
metal screw.
3. Replace air cleaner on engine and check operation
of vacuum motor and control dam per assembly.
TEMPERATURE SENSOR REPLACEMENT
Removal
1. Remove air cleaner from engine and disconnect
vacuum hose at sensor.
2. Pry up tabs of sensor retaining clip (fig. 15A).
NOTE: Observe position of sensor, new
sensor must be installed in this same position.
LIGHT DUTY TRUCK SERVICE MANUAL