Vacuum Advance Cto Valve; Vacuum Advance Cto Valve Replacement—Six-Cylinder Engine - Jeep J-10 Series 1982 Technical & Service Manual

PORT NO. 2
PORTD<
x=r
PORT NO. 1
Rg. 16-23 Vacuum Advance CTO Valve
70654
Functional Test
Connect a vacuum gauge to the center port (D) of the
CTO valve. Below 155°F (68°C) manifold vacuum should
be indicated on the gauge. Above 155°F (68°C) carbu
retor ported vacuum should be indicated on gauge.
Defective valves must be replaced.
NOTE: Ported vacuum is not available with the
throttle closed. Ported vacuum is only available when
the throttle is opened to achieve an engine speed of
approximately 1000 rpm.
Vacuum Advance Coolant Temperature Override (CTO)
Valve—Heavy-Duty Cooling System
General
This is a single function valve that is utilized in con
junction with a heavy-duty cooling system to prevent
overheating during high ambient temperature operating
conditions. It is connected to the engine coolant passage
in the same location as the CTO valve that is used with
standard cooling systems.
NOTE: Some engine applications utilize a heavy-duty
cooling system CTO valve in conjunction with a stan
dard cooling system CTO valve. Refer to Vacuum Dia
grams for actual applications.
Operation
When the coolant temperature is below the switching
temperature (220°F [104°C]), ported vacuum is exposed
at port 1 and applied to port D to allow ported vacuum to
control the distributor vacuum advance. When the cool
ant temperature reaches 220°F (104°C), port 1 closes
and port 2 is connected to port D to allow manifold
vacuum to control the distributor vacuum advance.
With manifold vacuum applied to the vacuum advance
mechanism, engine idle speed is increased thereby im
proving engine cooling efficiency and reducing coolant
boiling during idle speed engine operation.
IGNITION SYSTEMS 1G-33
Functional Test
(1) Connect vacuum gauge to port D (Dist) of heavy-
duty cooling system CTO valve. Below 220°F (104°C),
carburetor ported vacuum should be indicated on gauge.
(2) Above 220°F (104°C), port 1 (Carb) closes and
port 2 (Manifold) is connected to port D (Dist). Manifold
vacuum should now be indicated on gauge.
Vacuum Advance CTO Valve Replacement—Six-Cylinder
Engine
WARNING: If engine has been recently operated, use
care to prevent scalding by hot coolant System is
pressurized.
(1) Drain coolant from radiator. Use clean con
tainer so that coolant can be reused.
(2) Identify, tag and disconnect vacuum hoses from
CTO valve.
(3) Placedrain pan under enginebelowCTO valve.
WARNING: Use care to prevent scalding by hot cool
ant leaking from block whenremoving the valve.
(4) Using 7/8-inch open end wrench, remove valve
from intake manifold.
lostallitlon—Six-Cylinder
(5) Install replacement CTO valve.
(6) Connect vacuum hoses to valve.
(7) Install coolant.
NOTE: Remove temperature gauge sending unit from
cylinder head to aid in venting air while filling the
cooling system.
Vacuum Advance CTO Valve Replacement—Eight-Cylinder
Engine
WARNING: If engine has been recently operated, use
care to prevent scalding by hot coolant. System is
pressurized.
(1) Drain coolant from radiator. Use clean con
tainer so coolant can be reused.
(2) Remove air cleaner assembly.
(3) Identify, tag and disconnect vacuum hoses from
CTO valve.
(4) Using 7/8-inch open end wrench, remove CTO
valve from thermostat housing (or intake manifold).
(5) Install replacement CTO valve in thermostat
housing (or intake manifold).
(6) Connect vacuum hoses to valve.
(7) Install air cleaner assembly.
(8) Install coolant.
(9) Purge cooling system of air.