Regulated Vacuum Advance Control System; Forward Delay Valve; Non-Linear Vacuum Regulator Valve Operation - Jeep J-10 Series 1982 Technical & Service Manual

1G-34 IGNITION SYSTEMS
Regulated Vacuum Advance Control System
General
For all six- and eight-cylinder engines with a regu
lated vacuum advance control system, distributor vac
uum advance is primarily controlled by regulated
vacuum. The vacuum regulation is accomplished by the
use of a non-linear vacuum regulator valve (fig. 1G-24).
The ratio of the regulation (fig. 1G-25) is proportional to
the engine torque and rpm.
NOTE: The NL VRvalve operates in conjunction with a
CTO valve.
80806
Rg. 16-24 Non-Linear Vacuum Regulator (NLVR) Valve
^ — REGULATED VACUUM
PORTED VACUUM
— _ — MANIFOLD VACUUM
LOAD
90064
Rg. 16-25 Non-Linear Vacuum Regulator Valve Operation
Operation
The NLVR valve has two input ports (from manifold
vacuum and carburetor ported vacuum sources) and one
outlet port (to CTO valve). With no-torque or low-torque
engine operating conditions, the NLVR valve provides
regulated vacuum (fig. 1G-26). Under these conditions,
manifold vacuum is high and ported vacuum is either
non-existent or very low. The NLVR valve provides a
vacuum level that is somewhere between the two vac
uum levels. This is determined by the calibration of the
valve. As engine torque increases and ported vacuum
increases above the regulated value, the regulator valve
switches to ported vacuum.
m r -
NON-LINEAR
VACUUM
REGULATOR
VALVE (CARBURETOR
MANIFOLD PORTED
VACUUM VACUUM
H
S
*^-
cD
VI*
/
CTO
VALVE
/
REGULATED OR
MANIFOLD
VACUUM
(o o o
so o
DISTRIBUTOR
VACUUM ADVANCE
MECHANISM
90063
Rg. 16-26 Regulated Vacuum Advance Control System—Typical
Functional Test
Connect a vacuum gauge to the distributor port (D) of
the NLVR valve. With the engine at idle speed, a vac
uum level of approximately 7 in. Hg (24 kPa) should be
indicated on the gauge. As the throttle is opened and
engine speed increases, ported vacuum from the carbu
retor should be indicated on the vacuum gauge.
Replacement
(1) Identify, tag and disconnect vacuum hoses. Re
move NLVR valve.
(2) Connect vacuum hoses to replacement valve.
NOTE: Ensure vacuum hoses are connected to correct
valve ports.
Forward Delay Valve
Certain engines employ a one-way forward delay
valve (fig. 1G-27) in the vacuum advance circuit to im
prove driveability and also reduce undesirable hydro
carbon (HC) emission.
The valve functions to delay the effects of sudden
increases in vacuum during quick throttle closings and
thereby prevent sudden ignition advance during engine
deceleration.
Functional Test
(1) Connect external vacuum source to port on black
side of delay valve.
(2) Connect one end of 24-inch (60 cm) section of
rubber hose to vacuum gauge and other end to port on
colored side of valve.
(3) With elapsed time device in view and a constant
10 in. Hg (34 kPa) of vacuum applied, note time required
for gauge pointer to move from 0 to 8 in. Hg (0 to 27
kPa).
(4) Compare time to acceptable time limits listed in
Forward Delay Valve Time Limits chart.