jump start terminals JEEP CHEROKEE 1995 Service Repair Manual

²accessories being left on with the engine not run-
ning
²a faulty or improperly adjusted switch that allows
a lamp to stay on (see Ignition-Off Draw, in this
group).
INSPECTION
(1) Inspect condition of battery cable terminals,
battery posts, connections at engine block, starter so-
lenoid and relay. They should be clean and tight. Re-
pair as required.
(2) Inspect all fuses in the fuseblock module and
Power Distribution Center (PDC) for tightness in re-
ceptacles. They should be properly installed and
tight. Repair or replace as required.
(3) Inspect the electrolyte level in the battery. If
cell caps are removable, add water if required. If cell
caps are not removable, replace battery if electrolyte
level is low.
(4) Inspect generator mounting bolts for tightness.
Replace or tighten bolts, if required. Refer to Group
8B - Battery/Starter/Generator Service for torque
specifications.
(5) Inspect generator drive belt condition and ten-
sion. Tighten or replace belt as required. Refer to
Belt Tension Specifications in Group 7 - Cooling Sys-
tem.
(6) Inspect connections at generator field, battery
output, and ground terminals. Also check ground con-
nection at engine. They should all be clean and tight.
Repair as required.
OUTPUT WIRE RESISTANCE TEST
This test will show the amount of voltage drop
across the generator output wire, from the generator
battery terminal to the battery positive post.
PREPARATION
(1) Before starting test make sure vehicle has a
fully-charged battery. See Battery in this group for
more information.
(2) Turn ignition switch to OFF.
(3) Disconnect negative cable from battery.
(4) Disconnect generator output wire from genera-
tor battery output terminal.
(5) Connect a 0-150 ampere scale DC ammeter
(Fig. 2). Install in series between generator battery
output terminal and disconnected generator output
wire. Connect positive lead to generator battery out-
put terminal and negative lead to disconnected gen-
erator output wire.
(6) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to disconnected generator out-
put wire. Connect negative lead of test voltmeter to
battery positive cable at positive post.
(7) Connect one end of a jumper wire to ground
and with other end probe green K20 field wire at
back of generator (Fig. 2). This will generate a DTC.CAUTION: Do not connect green/orange A142 field
wire to ground. Refer to Group 8W - Wiring Dia-
grams for more information.
(8) Connect an engine tachometer, then connect
battery negative cable to battery.
(9) Connect a variable carbon pile rheostat be-
tween battery terminals. Be sure carbon pile is in
OPEN or OFF position before connecting leads. See
Load Test in this group for instructions.
TEST
(1) Start engine. Immediately after starting, re-
duce engine speed to idle.
(2) Adjust engine speed and carbon pile to main-
tain 20 amperes flowing in circuit. Observe voltmeter
reading. Voltmeter reading should not exceed 0.5
volts.
RESULTS
If a higher voltage drop is indicated, inspect, clean
and tighten all connections. This includes any con-
nection between generator battery output terminal
and battery positive post. A voltage drop test may be
performed at each connection to locate the connection
with excessive resistance. If resistance tests satisfac-
torily, reduce engine speed, turn OFF carbon pile and
turn OFF ignition switch.
(1) Disconnect negative cable from battery.
(2) Remove test ammeter, voltmeter, carbon pile,
and tachometer.
(3) Remove jumper wire.
(4) Connect generator output wire to generator
battery output terminal. Tighten nut to 8.561.5 Nzm
(75615 in. lbs.).
(5) Connect negative cable to battery.
(6) Use DRB scan tool to erase DTC.
CURRENT OUTPUT TEST
The generator current output test determines
whether generator can deliver its rated current out-
put.
PREPARATION
(1) Before starting test make sure vehicle has a
fully-charged battery. See Battery in this group for
more information.
(2) Disconnect negative cable from battery.
(3) Disconnect generator output wire at the gener-
ator battery output terminal.
(4) Connect a 0-150 ampere scale DC ammeter
(Fig. 3). Install in series between generator battery
output terminal and disconnected generator output
wire. Connect positive lead to generator battery out-
put terminal and negative lead to disconnected gen-
erator output wire.
8A - 18 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

(5) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to generator battery output ter-
minal.
(6) Connect negative lead of test voltmeter to a
good ground.
(7) Connect an engine tachometer, then connect
battery negative cable to battery.
(8) Connect a variable carbon pile rheostat be-
tween battery terminals. Be sure carbon pile is in
OPEN or OFF position before connecting leads. See
Load Test in this group for instructions.
(9) Connect one end of a jumper wire to ground
and with other end probe green K20 field wire at
back of generator (Fig. 3). This will generate a DTC.
CAUTION: Do not connect green/orange A142 field
wire to ground. Refer to Group 8W - Wiring Dia-
grams for more information.TEST
(1) Start engine. Immediately after starting, re-
duce engine speed to idle.
(2) Adjust carbon pile and engine speed in incre-
ments until a speed of 1250 rpm and voltmeter read-
ing of 15 volts is obtained.
CAUTION: Do not allow voltage meter to read above
16 volts.
(3) The ammeter reading must be within limits
shown in Generator Output Voltage Specifications.
RESULTS
(1) If reading is less than specified and generator
output wire resistance is not excessive, generator
should be replaced. Refer to Group 8B - Battery/
Starter/Generator Service.
CHARGING SYSTEM DIAGNOSIS
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 19

IGNITION SECONDARY CIRCUIT DIAGNOSIS
CHECKING FOR SPARK
CAUTION: When disconnecting a high voltage cable
from a spark plug or from the distributor cap, twist
the rubber boot slightly (1/2 turn) to break it loose
(Fig. 12). Grasp the boot (not the cable) and pull it
off with a steady, even force.
(1) Disconnect the ignition coil secondary cable
from center tower of the distributor cap. Hold the ca-
ble terminal approximately 12 mm (1/2 in.) from a
good engine ground (Fig. 13).
WARNING: BE VERY CAREFUL WHEN THE ENGINE
IS CRANKING. DO NOT PUT YOUR HANDS NEAR
THE PULLEYS, BELTS OR THE FAN. DO NOT WEAR
LOOSE FITTING CLOTHING.
(2) Rotate (crank) the engine with the starter mo-
tor and observe the cable terminal for a steady arc. If
steady arcing does not occur, inspect the secondary
coil cable. Refer to Spark Plug Cables in this group.
Also inspect the distributor cap and rotor for cracksor burn marks. Repair as necessary. If steady arcing
occurs, connect ignition coil cable to the distributor
cap.
(3) Remove a cable from one spark plug.
(4) Using insulated pliers, hold the cable terminal
approximately 12 mm (1/2 in.) from the engine cylin-
der head or block while rotating the engine with the
starter motor. Observe the spark plug cable terminal
for an arc. If steady arcing occurs, it can be expected
that the ignition secondary system is operating cor-
rectly.(note that if the ignition coil cable is re-
moved for this test, instead of a spark plug
cable, the spark intensity will be much higher.)
If steady arcing occurs at the spark plug cables, but
the engine will not start, connect the DRB scan tool.
Refer to the Powertrain Diagnostic Procedures ser-
vice manual.
FAILURE TO START TEST
To prevent unnecessary diagnostic time and wrong
test results, the previous Checking For Spark test
should be performed prior to this test.
WARNING: SET PARKING BRAKE OR BLOCK THE
DRIVE WHEELS BEFORE PROCEEDING WITH THIS
TEST.
(1) Unplug the ignition coil harness connector at
the coil (Fig. 14).
(2) Connect a set of small jumper wires (18 gauge
or smaller) between the disconnected harness termi-
nals and the ignition coil terminals. To determine po-
larity at connector and coil, refer to the Wiring
Diagrams section.
(3) Attach one lead of a voltmeter to the positive
(12 volt) jumper wire. Attach the negative side of
voltmeter to a good ground. Determine that sufficient
battery voltage (12.4 volts) is present for the starting
and ignition systems.
Fig. 12 Cable Removal
Fig. 13 Checking for SparkÐTypical
Fig. 14 Coil Harness ConnectorÐTypical (4.0L
Shown)
8D - 10 IGNITION SYSTEMSJ

temperature ranges. This depends upon the thick-
ness and length of the center electrodes porcelain in-
sulator.)
SPARK PLUG OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
25). The increase in electrode gap will be consider-
ably in excess of 0.001 inch per 1000 miles of opera-
tion. This suggests that a plug with a cooler heat
range rating should be used. Over advanced ignition
timing, detonation and cooling system malfunctions
can also cause spark plug overheating.
SPARK PLUG SECONDARY CABLES
TESTING
Spark plug cables are sometimes referred to as sec-
ondary ignition cables or secondary wires. The cables
transfer electrical current from the distributor to in-
dividual spark plugs at each cylinder. The spark plug
cables are of nonmetallic construction and have a
built in resistance. The cables provide suppression of
radio frequency emissions from the ignition system.Check the high-tension cable connections for good
contact at the ignition coil, distributor cap towers
and spark plugs. Terminals should be fully seated.
The terminals and spark plug covers should be in
good condition. Terminals should fit tightly to the ig-
nition coil, distributor cap and spark plugs. The
spark plug cover (boot) of the cable should fit tight
around the spark plug insulator. Loose cable connec-
tions can cause corrosion and increase resistance, re-
sulting in shorter cable service life.
Clean the high tension cables with a cloth moist-
ened with a nonflammable solvent and wipe dry.
Check for brittle or cracked insulation.
When testing secondary cables for damage with an
oscilloscope, follow the instructions of the equipment
manufacturer.
If an oscilloscope is not available, spark plug cables
may be tested as follows:
CAUTION: Do not leave any one spark plug cable
disconnected for longer than necessary during test-
ing. This may cause possible heat damage to the
catalytic converter. Total test time must not exceed
ten minutes.
With the engine not running, connect one end of a
test probe to a good ground. Start the engine and run
the other end of the test probe along the entire
length of all spark plug cables. If cables are cracked
or punctured, there will be a noticeable spark jump
from the damaged area to the test probe. The cable
running from the ignition coil to the distributor cap
can be checked in the same manner. Cracked, dam-
aged or faulty cables should be replaced with resis-
tance type cable. This can be identified by the words
ELECTRONIC SUPPRESSION printed on the cable
jacket.
Use an ohmmeter to test for open circuits, exces-
sive resistance or loose terminals. Remove the dis-
tributor cap from the distributor.Do not remove
cables from cap.Remove cable from spark plug.
Connect ohmmeter to spark plug terminal end of ca-
ble and to corresponding electrode in distributor cap.
Resistance should be 250 to 1000 Ohms per inch of
cable. If not, remove cable from distributor cap tower
and connect ohmmeter to the terminal ends of cable.
If resistance is not within specifications as found in
the Spark Plug Cable Resistance chart, replace the
cable. Test all spark plug cables in this manner.
Fig. 24 Preignition Damage
Fig. 25 Spark Plug Overheating
SPARK PLUG CABLE RESISTANCE
8D - 14 IGNITION SYSTEMSJ

(8) Disconnect jumper wires from relay and 12 Volt
power source.
If continuity or resistance tests did not pass, re-
place relay. If tests passed, refer to Group 8W, Wiring
Diagrams for additional circuit information. Also re-
fer to the appropriate Powertrain Diagnostic Proce-
dures manual for operation of the DRB scan tool.
STARTER MOTOR RELAY TEST
Refer to Group 8A, Battery/Starting/Charging/Sys-
tem Diagnostics, for starter motor relay testing.
FUEL INJECTOR TEST
To perform a complete test of the fuel injectors and
their circuitry, refer to DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the injector only, refer to the following:
Disconnect the injector wire connector from the in-
jector. Place an ohmmeter on the injector terminals.
Resistance reading should be approximately 14.5
ohms61.2 ohms at 20ÉC (68ÉF). Proceed to the fol-
lowing Injector Diagnosis chart.When performing
the following tests from the chart, do not leave
electrical current applied to the injector for
longer than five seconds. Damage to injector
coil or internal injector seals could result.
FUEL SYSTEM PRESSURE TEST
Refer to the Fuel Delivery System section of this
group. See Fuel System Pressure Test.
ON-BOARD DIAGNOSTICS (OBD)
The powertrain control module (PCM) has been
programmed to monitor many different circuits of the
fuel injection system. If a problem is sensed in a
monitored circuit often enough to indicate an actual
problem, a Diagnostic Trouble Code (DTC) is stored.
The DTC will be stored in the PCM memory for even-
tual display to the service technician. If the problem
is repaired or ceases to exist, the PCM cancels the
DTC after 51 engine starts.Certain criteria must be met for a diagnostic trou-
ble code (DTC) to be entered into PCM memory. The
criteria may be a specific range of engine rpm, engine
temperature and/or input voltage to the PCM.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal-
function has occurred. This may happen because one
of the DTC criteria for the circuit has not been met.
Example: assume that one of the criteria for the
MAP sensor circuit is that the engine must be oper-
ating between 750 and 2000 rpm to be monitored for
a DTC. If the MAP sensor output circuit shorts to
ground when the engine rpm is above 2400 rpm, a 0
volt input will be seen by the PCM. A DTC will not
be entered into memory because the condition does
not occur within the specified rpm range.
A DTC indicates that the powertrain control mod-
ule (PCM) has recognized an abnormal signal in a
circuit or the system. A DTC may indicate the result
of a failure, but never identify the failed component
directly.
There are several operating conditions that the
PCM does not monitor and set a DTC for. Refer to
the following Monitored Circuits and Non-Monitored
Circuits in this section.
MONITORED CIRCUITS
The powertrain control module (PCM) can detect
certain problems in the fuel injection system.
Open or Shorted Circuit- The PCM can deter-
mine if sensor output (which is the input to PCM) is
within proper range. It also determines if the circuit
is open or shorted.
Output Device Current Flow- The PCM senses
whether the output devices are hooked up.
If there is a problem with the circuit, the PCM
senses whether the circuit is open, shorted to ground
(-), or shorted to (+) voltage.
Oxygen Sensor- The PCM can determine if the
oxygen sensor is switching between rich and lean.
This is, once the system has entered Closed Loop. Re-
fer to Open Loop/Closed Loop Modes Of Operation in
the Component Description/System Operation section
for an explanation of Closed (or Open) Loop opera-
tion.
NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems or conditions that could have malfunctions
that result in driveability problems. A Diagnostic
Trouble Code (DTC) may not be displayed for these
conditions.
Fuel Pressure:Fuel pressure is controlled by the
vacuum assisted fuel pressure regulator. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, or a pinched fuel supply or return
Fig. 44 Fuel Injector Internal ComponentsÐTypical
JFUEL SYSTEM GENERAL DIAGNOSIS 14 - 51

HEATING AND AIR CONDITIONING TEST PROCEDURES
INDEX
page page
A/C Compressor Clutch..................... 15
A/C Compressor Clutch Relay................ 15
A/C Compressor Clutch Relay................ 16
Air Conditioning ControlsÐXJ Vehicles......... 15
Air Conditioning ControlsÐYJ Vehicles......... 16
Blower Motor............................ 17
Blower Motor Switch....................... 16Compressor Clutch........................ 16
Fin Sensing Cycling Clutch Switch............. 15
Heater Diagnosis......................... 17
Low-Pressure High-Pressure Cut-Off Switch..... 15
Low-Pressure High-Pressure Cut-Off Switch..... 16
Thermostatic Control....................... 16
AIR CONDITIONING CONTROLSÐXJ VEHICLES
The A/C Compressor Clutch is controlled by several
components: the Pressure Cut-Off Switch, Cycling
Clutch Switch, Clutch Relay and Powertrain Control
Module (PCM).
Powertrain Control Module may delay A/C clutch
engagement up to 30 seconds.
Refer to Group 8W Wiring Diagrams for wiring and
terminals. Use volt ohmmeter to test switches.
A/C COMPRESSOR CLUTCH
The clutch assembly consists of a stationary elec-
tromagnetic coil, hub bearing pulley assembly, and
clutch plate. When the coil is energized the plate is
magnetically engaged with the pulley and turns the
compressor shaft.
A/C COMPRESSOR CLUTCH TEST
(1) Unplug clutch coil connector.
(2) Connect a jumper wire from the battery posi-
tive post to the clutch coil terminal. The clutch
should engage, if not leave jumper wire connected
and go to next step.
(3) Connect a jumper wire from clutch coil frame to
chassis ground. The clutch should engage if not re-
pair clutch coil ground or replace coil.
A/C COMPRESSOR CLUTCH RELAY
The A/C compressor clutch relay controls the 12-
volt source to the A/C clutch. The relay is activated
when the PCM receives a A/C request signal from the
fin-sensed cycling clutch switch. The PCM then sends
a ground signal to the relay. The relay is activated
and sends 12-volts to the clutch coil which energizes
the clutch. The relay is located in the power distribu-
tion center.
COMPRESSOR CLUTCH RELAY TEST
For test procedure refer to Powertrain Diagnostic
Service Manual for A/C clutch relay circuit test.
LOW-PRESSURE HIGH-PRESSURE CUT-OFF
SWITCH
The pressure cut-off switch is located on the filter
drier and is wired in series with compressor clutch.
The switch interrupts the power to the compressor
clutch circuit when the pressure drops to 193 kPa (28
psi) or increases above 3100 to 3375 kPa (450 to 490
psi).
PRESSURE CUT-OFF SWITCH TEST
(1) Verify system has correct refrigerant charge.
(2) Turn ignition switch to RUN, A/C blower switch
to ON and control set to MAX.
(3) Unplug pressure cut-off switch and test feed
circuit from select switch. It should be battery volt-
age if not, repair open to select switch.
(4) Test for continuity between the switch termi-
nals. If continuity is not present recover refrigerant
from the system. Replace switch, evacuate and re-
charge system.
FIN SENSING CYCLING CLUTCH SWITCH
The switch is attached to the evaporator coil with
the temperature sensing probe inserted into the coil
fins. This switch prevents condensate water on the
evaporator coil from freezing. It does this by sending
signals to the PCM to cycling the compressor clutch
on and off.
FIN-SENSED CYCLING CLUTCH SWITCH TEST
Test area ambient temperature should be around
21ÉC (70ÉF) for test.
(1) Verify system has correct refrigerant charge.
(2) Start Engine and turn on A/C.
(3) If the compressor clutch cycles ON and OFF 2
to 3 times per minute the cycling clutch switch is
normal. The ambient temperature should be between
20ÉC-30ÉC (68ÉF-90ÉF). Above 32ÉC (90ÉF) the com-
pressor clutch may stay engaged (non cycling) due to
the high heat load, this condition is normal. If the
compressor clutch fails to engage go to next step.
(4) Disconnect wiring harness connector from
switch. With a volt meter test feed circuit from cut-
JHEATING AND AIR CONDITIONING 24 - 15