DIAGNOSTICS
SERVICE MANUAL NUMBER 24
Page 5G-38
90-861327--1 OCTOBER 1999
Chart A-7 (1 of 6): Ignition System Check
MEFI 1, MEFI 2 AND MEFI 3 BLACK SCORPION:
902 RED
B
A
3 PNK
121 BRN OR GRY
121 WHT
IC MODULE
ECM
MEFI 1
MEFI 2
J2-23
J2-8
J2-24
J2-6
MEFI 3
J1-10
J2-10
J1-24
J1-3
COIL
B+
DISTRIBUTOR
E
D
C
B
A
121 WHT
112 DK GRN
31 TAN
931 BRN
931 BRN
3 PNK
31 TAN
NOT USED
HARNESS CONNECT
OR
TO IGN
J2-11
J2-27
J1-6
CIRCUIT DESCRIPTION MEFI 1, MEFI 2 AND MEFI 3 BLACK SCORPION:
The Distributor Ignition (Dl) system receives supply voltage from the system relay through
CKT 902 to the ignition coil gray connector “B”. Inside the ignition coil, the gray connector
terminal “B” is connected to the black connector terminal “B.” Supply voltage is delivered
from the ignition coil black connector terminal “B” to the distributor Ignition Control (IC) mod-
ule “+” terminal through CKT 3.
Inside the distributor, the pick-up coil and pole piece will produce a voltage signal for cylinder
spark. The voltage signals are processed in the IC module and sent to the ECM. The ECM
will decide if the engine is in the cranking or running mode and adjust timing accordingly.
The voltages or signals are sent between the ECM and the IC module through CKT’s 423,
430, and 424. CKT 453 is the ground circuit.
The IC module will send the voltage signal to the ignition coil black connector terminal “A”
through CKT 121. The signal will trigger the coil creating secondary spark to be produced.
This secondary spark is sent to the distributor by a high tension lead.
Index