Engine - Jeep 1996 Grand Cherokee Service Manual

ZJ
DESCRIPTION AND OPERATION (Continued)
IGNITION SWITCH AND KEY LOCK CYLINDER
The ignition switch is located on the steering col-
umn. The Key-In-Switch is located in the ignition
switch module. For diagnosis of the Key-In-Switch,
refer to Group, 8U.
A column shift interlock device is used to lock the
transmission shifter in the Park position when the
key is in the Off position. The interlock device is
located within the steering column assembly and is
not servicable. If repair is necessary, the steering col-
umn assembly must be replaced. Refer to Group 19,
Steering for procedures.
DIAGNOSIS AND TESTING
AUTOMATIC SHUTDOWN (ASD) RELAY TEST
To perform a complete test of this relay and its cir-
cuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the relay only, refer to Relays—Opera-
tion/Testing in the Group 14, Fuel Systems section.
TESTING FOR SPARK AT COIL
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. 6). Grasp the boot (not the cable) and
pull it off with a steady, even force.
Fig. 6 Cable Removal
(1) Disconnect the ignition coil secondary cable
from center tower of the distributor cap. Hold the
cable terminal approximately 12 mm (1/2 in.) from a
good engine ground (Fig. 7).
WARNING: BE VERY
ENGINE IS CRANKING. DO NOT PUT YOUR HANDS
NEAR THE PULLEYS, BELTS OR THE FAN. DO NOT
WEAR LOOSE FITTING CLOTHING.
CAREFUL WHEN THE
Fig. 7 Checking for Spark—Typical
(2) Rotate (crank) the engine with the starter
motor and observe the cable terminal for a steady
arc. If steady arcing does not occur, inspect the sec-
ondary coil cable. Refer to Spark Plug Cables in this
group. Also inspect the distributor cap and rotor for
cracks or burn marks. Repair as necessary. If steady
arcing occurs, connect ignition coil cable to the dis-
tributor 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. (If the ignition coil cable is removed 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 appropriate Powertrain Diagnostic Procedures
service manual.
IGNITION COIL TEST
To perform a complete test of the ignition coil and
its circuitry, refer to the DRB scan tool. Also refer to
the appropriate Powertrain Diagnostics Procedures
manual. To test the coil only, refer to the following:
The ignition coil (Fig. 8) is designed to operate
without an external ballast resistor.
Inspect the ignition coil for arcing. Test the coil
according to coil tester manufacturer's instructions.
Test the coil primary and secondary resistance.
Replace any coil that does not meet specifications.
Refer to the Ignition Coil Resistance chart.
If the ignition coil is being replaced, the secondary
spark plug cable must also be checked. Replace cable
if it has been burned or damaged.
IGNITION SYSTEM 8D - 5