Jeep 1987 Wrangler Workshop Manual page 634

ELECTRICAL
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IGNITION SYSTEM - MOTORCRAFT (6-Cyl. Engine)
INTERMITTENT FAILURE DIAGNOSIS (cont'd.)
Condition Possible C a u s e Correction
ENGINE D O E S NOT
O P E R A T E SMOOTHLY
AND OR ENGINE MIS-
F I R E S AT HIGH S P E E D
(1) Spark plugs fouled or faulty.
(2) Ignition wires faulty (including
electronic retard).
(3) Spark advance system(s) faulty.
(4) S-terminal shorted to starter S -
terminal in solenoid.
(5) Trigger wheel pin missing.
(6) Ignition wires not connected in
correct firing order.
(7) Two plug wires of consecutive
firing cylinders routed next to
each other.
(1) Clean and gap plugs. Replace as
required.
(2) Check wires. Replace as required.
(3) Check operation. Repair as
required.
(4) Replace solenoid.
(5) Install pin.
(6) Connect wires correctly.
(7) Re-route plug wires away from
each other.
E X C E S S I V E F U E L C O N -
SUMPTION
(1) Incorrect ignition timing.
(2) Spark advance system(s) faulty.
(3) MCU (microprocessor) faulty.
(1) Check timing. Adjust as required.
(2) Check operation. Repair as
required.
(3) Test system. Repair as required.
E R R A T I C TIMING
ADVANCE
(1) Faulty vacuum advance
mechanism.
(2) Centrifugal advance weights
sticking.
(1) Check operation. Replace if
required.
• (2) Remove dirt, corrosion.
TIMING NOT A F F E C T E D
BY VACUUM
(1) Defective vacuum advance
mechanism.
(2) Vacuum advance mechanism
adjusting screws too far coun-
terclockwise.
(3) Pickup coil pviot corroded.
(1) Replace vacuum advance
mechanism.
(2) Turn screw clockwise to bring
advance within specifications
(Chapter 1A).
(3) Clean pivot.
INTERMITTENT
OPERATION
(1) Loose or corroded terminals
(2) Defective pickup coil.
(3) Defective control unit.
(4) Loose ground connector in dis-
tributor.
(5) Wires to distributor shorted
together or to ground.
(6) Trigger wheel pin missing.
(1) Tighten terminals, remove corro-
sion, apply eletrical grease.
(2) Perform pickup coil test.
(3) Perform control unit tests.
(4) Clean and tighten ground
connection.
(5) Check for frayed, pinched, or
burned wires.
(6) Install new pin.
708660
C-96