Page 1
DR SPEED CONTROL 8P - 1
SPEED CONTROL
TABLE OF CONTENTS
page page
SPEED CONTROL
DESCRIPTION ..........................1
OPERATION ............................2
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - VACUUM
SUPPLY TEST .........................2
DIAGNOSIS AND TESTING - ROAD TEST ....3
SPECIFICATIONS
TORQUE - SPEED CONTROL .............3
CABLE
DESCRIPTION ..........................3
OPERATION ............................3
REMOVAL .............................3
INSTALLATION ..........................6
SERVO
DESCRIPTION ..........................6
SPEED CONTROL
DESCRIPTION
All 3.7L/4.7L/5.9L/8.0LGas Engines and/or Diesel
With Automatic Trans.
The speed control system is operated by the use of
a cable and a vacuum controlled servo. Electronic
control of the speed control system is integrated into
the Powertrain Control Module (PCM). The controls
consist of two steering wheel mounted switches. The
switches are labeled: ON/OFF, RES/ACCEL, SET,
COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIPPERY.
OPERATION ............................7
REMOVAL .............................7
INSTALLATION ..........................7
SWITCH
DESCRIPTION ..........................8
OPERATION ............................8
REMOVAL .............................9
INSTALLATION ..........................9
VACUUM RESERVOIR
DESCRIPTION ..........................9
OPERATION ............................9
DIAGNOSIS AND TESTING - VACUUM
RESERVOIR ..........................9
REMOVAL .............................10
INSTALLATION .........................10
switches are labeled: ON/OFF, RES/ACCEL, SET,
COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIPPERY.
5.9L Diesel With Manual Trans.
The speed control system is fully electronically con-
trolled by the Engine Control Module (ECM). A
cable and a vacuum controlled servo are not
used if the vehicle is equipped with a manual
transmission and a diesel engine. This is a servo-less system. The controls consist of two steering
wheel mounted switches. The switches are labeled:
ON/OFF, RES/ACCEL, SET, COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
5.7L Gas
The speed control system is fully electronically con-
trolled by the Powertrain Control Module (PCM). A
cable and a vacuum controlled servo are not
used. This is a servo-less system. The controls
consist of two steering wheel mounted switches. The
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIPPERY.
Page 2
8P - 2 SPEED CONTROL DR
SPEED CONTROL (Continued)
OPERATION
When speed control is selected by depressing the
ON switch, the PCM (the ECM with a diesel engine)
allows a set speed to be stored in its RAM for speed
control. To store a set speed, depress the SET switch
while the vehicle is moving at a speed between 35
and 85 mph. In order for the speed control to engage,
the brakes cannot be applied, nor can the gear selector be indicating the transmission is in Park or Neutral.
The speed control can be disengaged manually by:
• Stepping on the brake pedal
• Depressing the OFF switch
• Depressing the CANCEL switch.
• Depressing the clutch pedal (if equipped).
NOTE: Depressing the OFF switch or turning off the
ignition switch will erase the set speed stored in
the PCM (the ECM with a diesel engine).
For added safety, the speed control system is programmed to disengage for any of the following conditions:
• An indication of Park or Neutral
• A rapid increase rpm (indicates that the clutch
has been disengaged)
• Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
• The speed signal increases at a rate of 10 mph
per second (indicates that the coefficient of friction
between the road surface and tires is extremely low)
• The speed signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
Once the speed control has been disengaged,
depressing the RES/ACCEL switch (when speed is
greater than 30 mph) restores the vehicle to the target speed that was stored in the PCM (the ECM with
a diesel engine).
While the speed control is engaged, the driver can
increase the vehicle speed by depressing the RES/ACCEL switch. The new target speed is stored in the
PCM (the ECM with a diesel engine) when the RES/
ACCEL is released. The PCM also has a 9tap-up9 feature in which vehicle speed increases at a rate of
approximately 2 mph for each momentary switch
activation of the RES/ACCEL switch.
A “tap down” feature is used to decelerate without
disengaging the speed control system. To decelerate
from an existing recorded target speed, momentarily
depress the COAST switch. For each switch activation, speed will be lowered approximately 1 mph.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - VACUUM SUPPLY
TEST
3.7L / 4.7L / 5.9L / 8.0L Gas Powered Engines
3.7L/4.7L/5.9L/8.0L gas powered engines: actual
engine vacuum, a vacuum reservoir, a one-way check
valve and vacuum lines are used to supply vacuum to
the speed control servo.
(1) Disconnect vacuum hose at speed control servo
and install a vacuum gauge into the disconnected
hose.
(2) Start engine and observe gauge at idle. Vacuum gauge should read at least ten inches of mercury.
(3) If vacuum is less than ten inches of mercury,
determine source of leak. Check vacuum line to
engine for leaks. Also check actual engine intake
manifold vacuum. If manifold vacuum does not meet
this requirement, check for poor engine performance
and repair as necessary.
(4) If vacuum line to engine is not leaking, check
for leak at vacuum reservoir. To locate and gain
access to reservoir, refer to Vacuum Reservoir Removal/Installation in this group. Disconnect vacuum line
at reservoir and connect a hand-operated vacuum
pump to reservoir fitting. Apply vacuum. Reservoir
vacuum should not bleed off. If vacuum is being lost,
replace reservoir.
(5) Verify operation of one-way check valve and
check it for leaks.
(a) Locate one-way check valve. The valve is
located in vacuum line between vacuum reservoir
and engine vacuum source. Disconnect vacuum
hoses (lines) at each end of valve.
(b) Connect a hand-operated vacuum pump to
reservoir end of check valve. Apply vacuum. Vacuum should not bleed off. If vacuum is being lost,
replace one-way check valve.
(c) Connect a hand-operated vacuum pump to
vacuum source end of check valve. Apply vacuum.
Vacuum should flow through valve. If vacuum is
not flowing, replace one-way check valve. Seal the
fitting at opposite end of valve with a finger and
apply vacuum. If vacuum will not hold, diaphragm
within check valve has ruptured. Replace valve.
5.7 Gas
Vacuum is not used for any part of the speed con-
trol system if equipped with a 5.7L V-8 engine.
5.9L Diesel Engine With Manual Trans.
Vacuum is not used for any part of the speed con-
trol system if equipped with a diesel engine and a
manual transmission.
Page 3
DR SPEED CONTROL 8P - 3
SPEED CONTROL (Continued)
5.9L Diesel Engines With Automatic Trans.
If equipped with a diesel powered engine and an
automatic transmission, an electric vacuum pump
and vacuum lines are used to supply vacuum to the
speed control servo. A vacuum reservoir is not used.
DIAGNOSIS AND TESTING - ROAD TEST
Perform a vehicle road test to verify reports of
speed control system malfunction. The road test
should include attention to the speedometer. Speedometer operation should be smooth and without flutter at all speeds.
Flutter in the speedometer indicates a problem
which might cause surging in the speed control system. The cause of any speedometer problems should
be corrected before proceeding. Refer to Instrument
Cluster for speedometer diagnosis.
If a road test verifies a system problem and the
speedometer operates properly, check for:
• A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
• A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
• Loose, damaged or corroded electrical connections at the servo (if used). Corrosion should be
removed from electrical terminals and a light coating
of Mopar MultiPurpose Grease, or equivalent,
applied.
• Leaking vacuum reservoir (if used).
• Loose or leaking vacuum hoses or connections (if
used).
• Defective one-way vacuum check valve (if used).
• Secure attachment of both ends of the speed con-
trol servo cable (if used).
• Smooth operation of throttle linkage (if used)
and throttle body air valve.
• Failed speed control servo (if used). Do the servo
vacuum test.
CAUTION: When test probing for voltage or continuity at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.
SPECIFICATIONS
TORQUE - SPEED CONTROL
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Servo Mounting Bracket-
to-Servo Nuts
Servo Mounting Bracket-
to-Battery Tray Screws
Speed Control Switch
Mounting Screws
Vacuum Reservoir
Mounting Nuts
7-60
4-30
1.7 - 15
3-20
CABLE
DESCRIPTION
The speed control servo cable is connected between
the speed control vacuum servo diaphragm and the
throttle body control linkage. This cable is used with
3.7L/4.7L/5.9L/8.0L gas powered engines only. It is
also used if equipped with a 5.9L diesel engine
equipped with an automatic transmission.
A speed control servo cable is not used if equipped
with either a 5.9L diesel engine equipped with a
manual transmission, or any 5.7L engine/transmission combinations.
OPERATION
This cable causes the throttle control linkage to
open or close the throttle valve in response to movement of the vacuum servo diaphragm.
REMOVAL
3.7L / 4.7L GAS
(1) Disconnect negative battery cable at battery.
(2) Remove air intake tube at top of throttle body.
The accelerator cable must be partially removed to
gain access to speed control cable.
Page 4
8P - 4 SPEED CONTROL DR
CABLE (Continued)
(3) Hold throttle in wide open position. While held
in this position, slide throttle cable pin (Fig. 1) from
throttle body bellcrank.
(4) Using a pick or small screwdriver, press release
tab (Fig. 2) to release plastic cable mount from
bracket. Press on tab only enough to release
cable from bracket. If tab is pressed too much,
it will be broken. Slide plastic mount (Fig. 2)
towards right side of vehicle to remove throttle cable
from throttle body bracket.
(5) Using finger pressure only, disconnect servo
cable connector (Fig. 3) at throttle body bellcrank pin
by pushing connector off bellcrank pin towards front
of vehicle. DO NOT try to pull connector off per-
pendicular to the bellcrank pin. Connector will
be broken.
(6) Slide speed control cable plastic mount towards
right of vehicle to remove cable from throttle body
bracket (Fig. 4).
(7) Remove servo cable from servo. Refer to Servo
Removal/Installation.
Fig. 2 THROTTLE CABLE RELEASE TAB - 3.7L /
4.7L
1 - THROTTLE CABLE
2 - RELEASE TAB
3 - PICK OR SCREWDRIVER
4 - PLASTIC CABLE MOUNT
Fig. 1 THROTTLE CABLE PIN - 3.7L / 4.7L
1 - THROTTLE CABLE PIN
2 - THROTTLE BODY BELLCRANK
3 - PUSH UP HERE
5.9L Gas
(1) Disconnect negative battery cable at battery.
(2) Remove air intake tube at top of throttle body.
(3) Using finger pressure only, remove speed control cable connector at bellcrank by pushing connector rearward off the bellcrank pin (Fig. 5). DO NOT
try to pull connector off perpendicular to the
bellcrank pin. Connector will be broken.
(4) Squeeze 2 tabs on sides of speed control cable
at throttle body mounting bracket (locking plate) and
push out of bracket.
Fig. 3 SPEED CONTROL CABLE AT BELLCRANK -
3.7L / 4.7L
1 - THROTTLE BODY BELLCRANK
2 - SPEED CONTROL CABLE CONNECTOR
(5) Remove servo cable from servo. Refer to Speed
Control Servo Removal/Installation in this group.
Page 5
DR SPEED CONTROL 8P - 5
CABLE (Continued)
Fig. 5 SERVO CABLE AT THROTTLE BODY - 5.9L
GAS
1 - VEHICLE SPEED CONTROL CABLE
8.0L Gas
(1) Disconnect negative battery cable at battery.
(2) Using finger pressure only, remove speed con-
trol cable connector at bellcrank by pushing connec-
Fig. 4 SPEED CONTROL CABLE AT BRACKET - 3.7L
/ 4.7L
1 - THROTTLE CABLE BRACKET
2 - PLASTIC CABLE MOUNT
3 - SPEED CONTROL CABLE
tor off the bellcrank pin (Fig. 6). DO NOT try to
pull connector off perpendicular to the
bellcrank pin. Connector will be broken.
(3) Squeeze 2 tabs on sides of speed control cable
at throttle body mounting bracket (locking plate) and
push out of bracket.
Fig. 6 SERVO CABLE AT THROTTLE BODY — 8.0L V-10 ENGINE
1 - THROTTLE CABLE
2 - THROTTLE VALVE CABLE
3 - SPEED CONTROL SERVO CABLE
Page 6
8P - 6 SPEED CONTROL DR
CABLE (Continued)
(4) Remove servo cable from servo. Refer to Speed
Control Servo Removal/Installation in this group.
5.9L Diesel — Auto. Trans.
(1) Disconnect both negative battery cables at both
batteries.
(2) Remove cable/lever/linkage cover. Refer to
Speed Control Servo Removal/Installation.
(3) Remove (disconnect) servo cable from servo.
Refer to Speed Control Servo Removal/Installation.
(4) Using finger pressure only, disconnect end of
servo cable from throttle lever pin by pulling forward
on connector while holding lever rearward (Fig. 7).
DO NOT try to pull connector off perpendicular
to lever pin. Connector will be broken.
(5) Squeeze 2 pinch tabs (Fig. 7) on sides of speed
control cable at mounting bracket and push cable
rearward out of bracket.
(6) Remove cable from vehicle.
(3) Install speed control cable connector onto throttle body bellcrank pin (push rearward to snap into
location).
(4) Slide throttle (accelerator) cable plastic mount
into throttle body bracket. Continue sliding until
cable release tab is aligned to hole in throttle body
mounting bracket.
(5) While holding throttle to wide open position,
place throttle cable pin into throttle body bellcrank.
(6) Install air intake tube to top of throttle body.
(7) Connect negative battery cable at battery.
(8) Before starting engine, operate accelerator
pedal to check for any binding.
5.9L / 8.0L Gas
(1) Install end of cable to speed control servo.
Refer to Speed Control Servo Removal/Installation.
(2) Install cable into throttle body mounting
bracket. Cable snaps into bracket.
(3) Install speed control cable connector at throttle
body bellcrank pin. Connector snaps onto pin.
(4) Install air intake tube to top of throttle body
(except 8.0L).
(5) Connect negative battery cable to battery.
(6) Before starting engine, operate accelerator
pedal to check for any binding.
Fig. 7 SERVO CABLE AT THROTTLE LEVER — 5.9L
DIESEL
1 - PINCH (2) TABS
2 - CABLE MOUNTING BRACKET
3 - PINCH TABS (2)
4 - OFF
5 - THROTTLE CABLE
6 - THROTTLE LEVER
7 - THROTTLE LEVER PIN
8 - OFF
9 - CONNECTOR
10 - SPEED CONTROL CABLE
INSTALLATION
3.7L / 4.7L Gas
(1) Install end of cable to speed control servo.
Refer to Servo Removal/Installation.
(2) Slide speed control cable plastic mount into
throttle body bracket.
5.9L Diesel — Auto. Trans.
(1) Install (connect) end of speed control servo
cable to speed control servo. Refer to Speed Control
Servo Removal/Installation.
(2) Install cable through mounting hole on mounting bracket. Cable snaps into bracket.
(3) Connect servo cable to throttle lever by pushing cable connector rearward onto lever pin while
holding lever forward.
Connect negative battery cables to both batteries.
(4)
(5) Before starting engine, operate accelerator
pedal to check for any binding.
(6) Install cable/lever cover.
SERVO
DESCRIPTION
A speed control servo is not used with any
5.7L V-8 engine, or with the 5.9L diesel engine
when equipped with a manual transmission.
The speed control servo is attached to the bottom
of the battery tray.
The servo unit consists of a solenoid valve body,
and a vacuum chamber. The solenoid valve body contains three solenoids:
• Vacuum
• Vent
• Dump
Page 7
DR SPEED CONTROL 8P - 7
SERVO (Continued)
The vacuum chamber contains a diaphragm with a
cable attached to control the throttle linkage.
OPERATION
A speed control servo is not used with any
5.7L V-8 engine, or with the 5.9L diesel engine
when equipped with a manual transmission.
The Powertrain Control Module (PCM) controls the
solenoid valve body. The solenoid valve body controls
the application and release of vacuum to the diaphragm of the vacuum servo. The servo unit cannot
be repaired and is serviced only as a complete assembly.
Power is supplied to the servo’s by the PCM
through the brake switch. The PCM controls the
ground path for the vacuum and vent solenoids.
The dump solenoid is energized anytime it receives
power. If power to the dump solenoid is interrupted,
the solenoid dumps vacuum in the servo. This provides a safety backup to the vent and vacuum solenoids.
The vacuum and vent solenoids must be grounded
at the PCM to operate. When the PCM grounds the
vacuum servo solenoid, the solenoid allows vacuum
to enter the servo and pull open the throttle plate
using the cable. When the PCM breaks the ground,
the solenoid closes and no more vacuum is allowed to
enter the servo. The PCM also operates the vent solenoid via ground. The vent solenoid opens and closes a
passage to bleed or hold vacuum in the servo as
required.
The PCM duty cycles the vacuum and vent solenoids to maintain the set speed, or to accelerate and
decelerate the vehicle. To increase throttle opening,
the PCM grounds the vacuum and vent solenoids. To
decrease throttle opening, the PCM removes the
grounds from the vacuum and vent solenoids. When
the brake is released, if vehicle speed exceeds 30
mph to resume, 35 mph to set, and the RES/ACCEL
switch has been depressed, ground for the vent and
vacuum circuits is restored.
(6) Disconnect servo cable at throttle body. Refer to
Servo Cable Removal/Installation.
(7) Remove 2 mounting nuts holding servo cable
sleeve to bracket (Fig. 9).
(8) Pull speed control cable sleeve and servo away
from servo mounting bracket to expose cable retaining clip (Fig. 9) and remove clip. Note: The servo
mounting bracket displayed in (Fig. 9) is a typical
bracket and may/may not be applicable to this model
vehicle.
(9) Remove servo from mounting bracket. While
removing, note orientation of servo to bracket.
Fig. 8 SPEED CONTROL SERVO LOCATION
1 - BATTERY TRAY
2 - MOUNTING LUGS
3 - SERVO
4 - ELEC. CONNEC.
5 - MOUNTING SCREWS (3)
6 - MOUNTING BRACKET
7 - VACUUM LINE
REMOVAL
The speed control servo assembly is attached to the
bottom of the battery tray (Fig. 8).
(1) Disconnect negative battery cable at battery
(both cables at both batteries if diesel).
(2) To gain access to servo, remove plastic wheel-
house splash shield over left-front wheel.
(3) Disconnect vacuum line at servo (Fig. 8).
(4) Disconnect electrical connector at servo (Fig. 8).
(5) Remove 3 servo mounting screws (Fig. 8).
Depending on engine application, different sets of
mounting lugs (Fig. 8) are used to support servo to
battery tray. While removing, note proper lugs.
INSTALLATION
(1) Position servo to mounting bracket (Fig. 9).
(2) Align hole in cable connector with hole in servo
pin. Install cable-to-servo retaining clip (Fig. 9).
(3) Insert servo mounting studs through holes in
servo mounting bracket.
(4) Install 2 servo-to-mounting bracket nuts and
tighten. Refer to torque specifications.
(5) Position servo assembly to correct mounting
lugs on battery tray (Fig. 8) and install 3 screws.
Tighten 3 screws. Refer to torque specifications.
(6) Connect vacuum line at servo.
(7) Connect electrical connector at servo.
Page 8
8P - 8 SPEED CONTROL DR
SERVO (Continued)
OPERATION
When speed control is selected by depressing the
ON, OFF switch, the PCM (ECM for diesel) allows a
set speed to be stored in its RAM for speed control.
To store a set speed, depress the SET switch while
the vehicle is moving at a speed between approximately 35 and 85 mph. In order for the speed control
to engage, the brakes cannot be applied, nor can the
gear selector be indicating the transmission is in
Park or Neutral.
The speed control can be disengaged manually by:
• Stepping on the brake pedal
• Depressing the OFF switch
• Depressing the CANCEL switch.
The speed control can be disengaged also by any of
the following conditions:
Fig. 9 SERVO CABLE CLIP REMOVE/INSTALL —
TYPICAL
1 - SERVO MOUNTING NUTS (2)
2 - SERVO
3 - CABLE RETAINING CLIP
4 - SERVO CABLE AND SLEEVE
(8) Connect servo cable to throttle body. Refer to
servo Cable Removal/Installation.
(9) Install left-front wheel-well liner.
(10) Connect negative battery cable to battery
(connect both cables if diesel).
(11) Before starting engine, operate accelerator
pedal to check for any binding.
SWITCH
DESCRIPTION
Two separate switch pods operate the speed control
system. The steering-wheel-mounted switches use
multiplexed circuits to provide inputs to the PCM (to
the ECM for diesel) for ON, OFF, RESUME, ACCELERATE, SET, DECEL and CANCEL modes. Refer to
the owner’s manual for more information on speed
control switch functions and setting procedures.
The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
Depending on engine control computer (JTEC
having a 3– plug connector or NGC having a 4–
plug connector), 2 types of switches are used.
Both types of switches are internally and externally different. The switch used with the NGC
system has an attached pigtail lead. The switch
used with the JTEC system does not have an
attached pigtail lead.
• An indication of Park or Neutral
• The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
• Depressing the clutch pedal.
• Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
• The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
• If the actual speed is not within 20 mph of the
set speed
The previous disengagement conditions are pro-
grammed for added safety.
Once the speed control has been disengaged,
depressing the ACCEL switch restores the vehicle to
the target speed that was stored in the PCM’s RAM
(ECM for diesel).
NOTE: Depressing the OFF switch will erase the set
speed stored in the PCM’s RAM.
If, while the speed control is engaged, the driver
wishes to increase vehicle speed, the PCM (ECM for
diesel) is programmed for an acceleration feature.
With the ACCEL switch held closed, the vehicle
accelerates slowly to the desired speed. The new target speed is stored in the PCM’s RAM when the
ACCEL switch is released. The PCM also has a 9tapup9 feature in which vehicle speed increases at a rate
of approximately 2 mph for each momentary switch
activation of the ACCEL switch.
The PCM also provides a means to decelerate without disengaging speed control. To decelerate from an
existing recorded target speed, depress and hold the
COAST switch until the desired speed is reached.
Then release the switch. The ON, OFF switch operates two components: the PCM’s ON, OFF input, and
the battery voltage to the brake switch.
Page 9
DR SPEED CONTROL 8P - 9
SWITCH (Continued)
REMOVAL
Depending on engine control computer (JTEC
having a 3–plug connector or 5.7L V-8 NGC having a 4–plug connector), 2 types of switches are
used. Both types of switches are internally and
externally different. The switches used with the
NGC system have attached pigtail leads (Fig.
11). The switch used with the JTEC system does
not have an attached pigtail lead.
(1) Remove switch mounting screw (Fig. 10). or
(Fig. 11)
(2) Pull switch from steering wheel.
(3) Unplug electrical connector from switch (Fig.
10), or, switch pigtail wire harness from steering
wheel wire harness (Fig. 11) and remove switch.
Fig. 10 SPEED CONTROL SWITCHES (EXCEPT 5.7L
V-8 ENGINE)
1 - ELECTRICAL CONNECTORS
2 - MOUNTING SCREWS
3 - RIGHT SWITCH
4 - LEFT SWITCH
INSTALLATION
(1) Plug electrical connector into switch (Fig. 10),
or connect pigtail wire harness to steering wheel wire
harness (Fig. 11). Be sure wires are not pinched.
(2) Position switch to steering wheel.
(3) Install switch mounting screw and tighten.
Refer to torque specifications.
Fig. 11 SPEED CONTROL SWITCHES (WITH 5.7L V-8
ENGINE)
1 - MOUNTING SCREWS
2 - RIGHT SWITCH
3 - LEFT SWITCH
4 - PIGTAIL LEADS
VACUUM RESERVOIR
DESCRIPTION
The vacuum reservoir is a plastic storage tank connected to an engine vacuum source by vacuum lines.
A vacuum reservoir is not used with diesel engines or
the 5.7L gas powered engine.
OPERATION
The vacuum reservoir is used to supply the vacuum needed to maintain proper speed control operation when engine vacuum drops, such as in climbing
a grade while driving. A one-way check valve is used
in the vacuum line between the reservoir and the
vacuum source. This check valve is used to trap
engine vacuum in the reservoir. On certain vehicle
applications, this reservoir is shared with the heating/air-conditioning system. The vacuum reservoir
cannot be repaired and must be replaced if faulty.
DIAGNOSIS AND TESTING - VACUUM
RESERVOIR
(1) Disconnect vacuum hose at speed control servo
and install a vacuum gauge into the disconnected
hose.
Page 10
8P - 10 SPEED CONTROL DR
VACUUM RESERVOIR (Continued)
(2) Start engine and observe gauge at idle. Vacuum gauge should read at least ten inches of mercury.
(3) If vacuum is less than ten inches of mercury,
determine source of leak. Check vacuum line to
engine for leaks. Also check actual engine intake
manifold vacuum. If manifold vacuum does not meet
this requirement, check for poor engine performance
and repair as necessary.
(4) If vacuum line to engine is not leaking, check
for leak at vacuum reservoir. To locate and gain
access to reservoir, refer to Vacuum Reservoir Removal/Installation in this group. Disconnect vacuum line
at reservoir and connect a hand-operated vacuum
pump to reservoir fitting. Apply vacuum. Reservoir
vacuum should not bleed off. If vacuum is being lost,
replace reservoir.
(5) Verify operation of one-way check valve and
check it for leaks. Certain models may be
equipped with 2 check-valves.
(a) Locate one-way check valve. The valve is
located in vacuum line between vacuum reservoir
and engine vacuum source. Disconnect vacuum
hoses (lines) at each end of valve.
(b) Connect a hand-operated vacuum pump to
reservoir end of check valve. Apply vacuum. Vacuum should not bleed off. If vacuum is being lost,
replace one-way check valve.
(c) Connect a hand-operated vacuum pump to
vacuum source end of check valve. Apply vacuum.
Vacuum should flow through valve. If vacuum is
not flowing, replace one-way check valve. Seal the
fitting at opposite end of valve with a finger and
apply vacuum. If vacuum will not hold, diaphragm
within check valve has ruptured. Replace valve.
Fig. 12 VACUUM RESERVOIR LOCATION
1 - COWL GRILL
2 - WIPER ARMS / BLADES
3 - VACUUM RESERVOIR
REMOVAL
The vacuum reservoir is located in the engine com-
partment under the fresh air cowl grill panel (Fig.
12).
(1) Remove wiper blades and arms. Refer to Wiper
Arm Removal / Installation in the Wipers / Washers
section.
(2) Remove fresh air cowl grill. Refer to Cowl Grill
Removal / Installation.
(3) Disconnect vacuum line at reservoir (Fig. 13).
(4) Remove 2 reservoir mounting nuts (Fig. 13).
(5) Remove reservoir from cowl.
INSTALLATION
(1) Position reservoir onto 2 weld studs (Fig. 13).
(2) Install 2 mounting nuts and tighten. Refer to
torque specifications.
(3) Connect vacuum line to reservoir fitting.
(4) Install cowl grill. Refer to Cowl Grill Removal /
Installation.
Fig. 13 VACUUM RESERVOIR REMOVAL /
INSTALLATION
1 - COWL (BELOW WIPER ARMS)
2 - VACUUM LINE CONNECTION
3 - MOUNTING NUTS (2)
4 - VACUUM RESERVOIR
5 - WELDED STUDS
(5) Install wiper arms / blades. Refer to Wiper Arm
Removal / Installation.
Loading...