Diagnosis Of The Ignition System - GMC G Service Manual

6D-38 ENGINE ELECTRICAL

DIAGNOSIS OF THE IGNITION SYSTEM

DISTRIBUTOR/TIMING SYSTEM
FOR TBI-EQUIPPED ENGINES
CAUTION: To prevent possible injury from a
moving vehicle or operating engine, do the fol­
lowing before performing the checks:
1. Engage the parking brake and block the
wheels.
2. Place the automatic transmission in "PARK" or
the manual transmission in "NEUTRAL."
1. Refer to the Fuel and Emissions Service Manual for
information on the computerized ignition system,
including the diagnostic use of the "Check Engine" or
"Service Engine Soon" lamps.
2. Refer to the 1988 Light Duty Trucks Unit Repair Man­
ual for distributor component checks.
IGNITION SYSTEM FOR
CARBURETED ENGINES
CAUTION: To prevent possible injury from a
moving vehicle or operating engine, do the fol­
lowing before performing the checks:
Tool Required:
ST 125 Spark Plug Tester
1. Engage the parking brake and block the
wheels.
2. Place the automatic transmission in "PARK" or
the manual transmission in "NEUTRAL."
1. Refer to figure 49, 50 and 51 for system diagnosis.
2. Refer to the 1988 Light Duty Trucks Unit Repair Man­
ual for distributor component checks.