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6E-16
1977 PONTIAC SERVICE MANUAL
e. Remove hose from EGR valve and plug hose. Read
vacuum gage. This reading should be the same as or higher
than the source reading taken in step 2C.
Replace BPT valve if reading is not within 3 inches
of source reading from step 2C.
3. EGR THERMAL VACUUM VALVE
a. Refer to Section 6D (vacuum controls) for checking
temperature and procedures for the valve used on the engine
being serviced.
EGR SYSTEM
-
INSPECTION AND
CLEANING
The following procedure is to be used for the inspection
and cleaning of the EGR valve and passages.
Inspection
1. Remove air cleaner.
2. Remove EGR valve from intake manifold.
3. Look for deposits on the valve pintle.
4. Depress the valve diaphragm and inspect for deposits
around the valve seating area thru the valve outlet.
5. With the diaphragm still depressed, plug the vacuum
tube then release the diaphragm. If the pintle has not closed
in 20 seconds, the EGR valve is OK. If the pintle is closed
within 20 seconds, the valve must be replaced.
6. The valve requires cleaning if deposits exist.
Cleaning
1. Hold the valve assembly in hand. Then, using a light
snapping action with a plastic hammer, tap on the end of the
round pintle to remove the exhaust despoits from the valve
seat. Empty loose particles.
2. Clean the mounting surface of the EGR valve with
a wire wheel or wire brush, and the pintle with a wire brush.
3. Depress the valve diaphragm and check the seating
area for cleanliness by looking thru the valve outlet. If pintle
or seat are not completely clean, repeat step 1.
4. Inspect the valve outlet for deposits. Remove any
deposit build-up with a screwdriver or other suitable sharp
tool.
5. Clean mounting surface with a wire wheel or wire
brush.
NOTE: Do not use solvents for cleaning.
INTAKE MANIFOLD PASSAGES
1. Remove carburetor.
2. Remove the deposits from the EGR ports by hand
turning a drill into the passage. Finish cleaning with a small
screwdriver. Refer to Fig. 6E-26 for location of the EGR
ports on various engine types.
CAUTION: Do not use a power drill or file.
3. Brush any small particles down the EGR port and
blow compressed air through the port.
NOTE: Do not use solvents for cleaning.
POSITIVE CRANKCASE
VENTILATION SYSTEM
FUNCTIONAL TEST OF PCV SYSTEM
1. Remove PCV valve from intake manifold or rocker
arm cover.
2. Run the engine at idle.
3. Place your thumb over end of valve to check for
vacuum. If there is no vacuum at valve, check for plugged
hoses or valve.
4. Shut off the engine. Shake valve and listen for the
rattle of check needle in valve. If valve does not rattle, replace
valve.
THERMOSTATIC AIR CLEANER
VACUUM MOTOR CHECK
1. Check all hoses for proper hook-up. Check for kinked,
plugged or damaged hoses.
2. With the engine "OFF", observe damper door
position through snorkel opening. If position of snorkel
makes observation difficult, use the aid of a mirror. At this
point damper door should be in such a position that the heat
stove passage is covered (snorkel passage open). See Fig. 6E-
27. On V8-301 engines in cold temperatures the damper door
may be closed due to the use of a vacuum check valve.
Momentarily disconnect vacuum hose at TAC vacuum motor
and observe damper position. If stove passage is not covered,
check for binds in linkage.
3. Apply at least 7 in Hg. of vacuum to the diaphragm
assembly through hose disconnected at sensor unit. Damper
door should completely close snorkel passage when vacuum
is applied. See Fig. 6E-28. If not, check to see if linkage is
hooked up correctly and not binding and for a vacuum leak.
4. With vacuum applied, bend or clamp hose to trap
vacuum in diaphragm assembly. Damper door should remain
in position (closed snorkel passage), Fig. 6E-28
.
If it does
not, there is a vacuum leak in diaphragm assembly. Replace
diaphragm assembly.
SENSOR CHECK (QUICK CHECK OF
SYSTEM)
1. Start test with engine cold, air cleaner at a temperature
below 77°F. (25°C.). If the engine has been in recent use, allow
it to cool. (Removing the air cleaner from the engine and
placing it on the bench will aid in quickly cooling the sensor.)
On V8-301 engines, momentarily disconnect vacuum hose at
TAC vacuum motor before proceeding with test.
2. Observe the damper door before starting the engine:
it should be in the open snorkel position, Fig. 6E-27.
3. Start the engine and allow it to idle. Immediately after
starting the engine, the damper door should be in the closed
snorkel passage position, Fig. 6E-28.
4. As the engine warms up, the damper door should start
to allow outside air and heated air to enter the carburetor
inlet.
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