Dodge RAM TRUCK 1500 1995 Service Manual page 388

BR
IGNITION SYSTEMS 80-15
IGNITION SECONDARY CIRCUIT DIAGNOSIS
CHECKING FOR SPARK—EXCEPT 8.0L If-fO
ENGINE
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. 18). Grasp the boot (not the cable) and pull it
off with a steady, even force.
SPARK PLUG BOOT«
PULLER
SPARK PLUG
CABLE A N D
BOOT
TWIST AND PULL
SPARK PLUG
958D-9
Fig. 18 Cable Removal
(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. 19).
• O
o
O
CHECK HERE
FOR SPARK
IGNITION
c o , L 918D-18
Fig. 19 Checking for Spark—Typical
WARNING: B E V E R Y C A R E F U L W H E N THE ENGINE
IS CRANKING. DO NOT PUT YOUR HANDS N E A R
THE P U L L E Y S , B E L T S OR THE FAN. DO NOT W E A R
L O O S E 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 cracks
or 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—EXCEPT 8.0L V-fO
ENGINE
To prevent unnecessary diagnostic time and wrong
test results, the previous Checking For Spark test
should be performed prior to this test.
WARNING: S E T PARKING B R A K E OR B L O C K THE
DRIVE W H E E L S B E F O R E PROCEEDING WITH THIS
TEST.
(1) Unplug the ignition coil harness connector at
the coil (Figs. 20 or 21).
-«* COL
ffCONNECTOR J°214-7
Fig. 20 Coil Harness Connector—3.9L V-6 or
5.2/5.9L LDC-Gas Engines
(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