Ignition Coil Tests; Vacuum Advance Test; Primary Winding Resistance Test; Secondary Winding Resistance Test - Jeep 1987 Wrangler Workshop Manual

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IGNITION SYSTEM - MOTORCRAFT (6-Cyl. Engine)
WARNING: Use extreme caution when the
engine is operating. Do not stand in a direct line
with the fan. Do not put hands near the pulleys,
belts or fan. Do not wear loose clothing.
Start the engine and observe the timing degree
scale and index with the timing lamp while the
engine is idling.
Siowly increase the engine speed to 2000
rpm. The timing should advance smoothly as
engine speed increases. Refer to Chapter B -
Engines - General Service and Diagnosis for
mechanical advance curve information.
V a c u u m Adtance Test
NOTE: The engine must be warmed to normal
operating temperature.
Connect the vacuum hose to the vacuum
advance mechanism.
Observe the timing degree scale and index with
the timing lamp while the engine is at idle speed.
Slowly increase the engine speed to 2000
rpm. With vacuum applied, the ignition timing
should advance sooner than with the centri-
fugal advance alone. At 2000 rpm, the vacuum
advance should cause total advance to be
more than with the centrifugal advance alone.
Refer to Chapter B - Engines - General Ser-
vice and Diagnosis for vacuum advance
curve information.
IGNITION COIL TESTS
T h e ignition coil c a n be tested on any
conventional coil tester or with an ohmmeter. A
coil tester is preferable because it can be used to
detect faults that are impossible with an
ohmmeter.
Primary Wilding Resistance lest
Remove the connector from the negative ( - )
and positive ( + ) terminals of the ignition coil.
Set the ohmmeter for the low scale and adjust
the pointer to zero.
Connect the ohmmeter to the coil negative and
positive terminals. The resistance should be
1.13 - 1.23 ohms at 2 4 ° C ( 7 5 ° F ) . If the coil
temperature is above 9 3 ° C ( 2 0 0 ° F ) , 1.50 ohms
is acceptable.
Secondary Winding Resistance Test
Remove the high voltage ignition wire from the
high voltage terminal of the ignition coil.
NOTE: The ignition switch must be O F F .
Set the ohmmeter for the x1000 scale and adjust
the pointer to zero.
Connect the ohmmeter to the brass contact in
the high voltage terminal and to either primary
winding terminal. The resistance should be
7700 - 9300 ohms at 2 4 ° C ( 7 5 ° F ) . A maximum of
1 2 , 0 0 0 o h m s is a c c e p t a b l e if the coil
temperature is 9 3 ° C ( 2 0 0 ° F ) or more.
Current Flow Test
Remove the connector from the ignition coil.
Depress the plastic barb and withdraw the
positive ( + ) wire terminal from the connector.
The barb is visible from the coil side of the
connector.
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