Scope Analyzer Diagnosis - Ignition System Tester; Cylinder Compression Pressure Test - Jeep 1987 Wrangler Workshop Manual

ENGINES
GENERAL SERVICE AND DIAGNOSIS
SCOPE ANALYZER DIAGNOSIS
- IGNITION
SYSTEM TESTER
A scope analyzer is an ignition system tester
that provides a means for quick and accurate
diagnosis of ignition system performance
problems.
All phases of the ignition cycle are displayed
graphically on an oscilloscope (cathode ray
tube) as they occur during engine operation.
T h e m a n u f a c t u r e r s of s c o p e a n a l y z e r
equipment provide descriptions of the test
p r o c e d u r e s that are possible with their
equipment. This manual is not intended to
describe all the possible uses of scope analyzer
equipment, but to illustrate a typical display of
the Solid State Ignition (SSI) system.
CYLINDER COMPRESSION PRESSURE TEST
The results of a cylinder compression pressure
test can be utilized to diagnose several engine
malfunctions.
N O T E : E n s u r e the battery is completely
charged and the starter motor is in good
operating condition. Otherwise the indicated
compression pressures may not be valid for
diagnosis purposes.
Clean the spark plug recesses with compressed
air.
Remove the spark plugs.
Secure the throttle in the wide-open position.
SSI S Y S T E M
A S P A R K P L U G F I R E S
I
P R I M A R Y WINDING
I
E L E C T R O M A G N E T I C
, F I E L D C O L L A P S E S A N D
I
I N D U C E S H I G H V O L T A G E
| INTO S E C O N D A R Y
WINDING
U N U S E D C T R I G G E R D T R I G G E R
E N E R G Y • W H E E L I W H E E L
O S C I L L A T I O N S 1
T O O T H ,
T O O T H AP
G R A D U A L L Y
' S E P A
1 P R O A C H E S
D A M P E N
J
R A T E D
I A L I G N
' F R O M 1 M E N T W I T H
I P I C K U P
j T H E PICK
' C O I L * UP C O I L
1 NO | AND
' C U R R E N T '
P R I M A R Y
J F L O W |
WINDING
C U R R E N T
I N C R E A S E S
WHICH
R E S U L T S
IN LOW
V O L T A G E
B E I N G IN
D U C E D
I N T O T H E
S E C O N D A R Y
WINDING
C I R C U I T O P E N
NO C U R R E N T F L O W P R I O R
TO E L E C T R O M A G N E T I C
F I E L D C O L L A P S I N G
840111
B-18