Subject Page; Battery; Electrical System - GMC G Service Manual

6D-2 ENGINE ELECTRICAL
SUBJECT
Diagnosis of the Ignition System........................................................................................................................... 6D-38
Distributor/Timing System for TBI-Equipped Engines...................................................................................... 6D-38
Ignition System for Carbureted Engines.............................................................................................................6D-38
Diagnosis of Spark Plugs........................................................................................................................................ 6D-42
Ignition System On-Vehicle Service....................................................................................................................... 6D-43
Service Precautions.............................................................................................................................................. 6D-43
Distributor Replacement....................................................................................................................................... 6D-43
Ignition Timing....................................................................................................................................................... 6D-44
Spark Plug Wires................................................................................................................................................... 6D-45
Spark Plug Wire Replacement..............................................................................................................................6D-45
Engine Wire Harness................................................................................................................................................ 6D-53
Specifications............................................................................................................................................................ 6D-78
Special Tools............................................................................................................................................................. 6D-81
Engine electrical system diagnosis includes the battery,
charging system (generator and related wiring), cranking
system (starter and related wiring), ignition system (distrib­
utor, spark plugs and wiring) and the glow plug system
(diesel electrical).
Light duty emission vehicles are equipped with an elec­
tronic computer command control system. These vehicles
DESCRIPTION
The battery has three major functions in the electrical
system: first, it provides a source of energy for cranking the
engine; second, it acts as a voltage stabilizer for the electri­
cal system; and third, it can, for a limited time, provide
energy when the electrical load used exceeds the output of
the generator.
The sealed battery as shown in figure 1 is standard.
Water never needs to be added. There are no filler caps in
the cover. The battery is sealed, except for small vent holes
in the cover. The vents allow the escape of whatever small
amount of gases that are produced in the battery. The spe­
cial chemical composition inside the battery reduces gas­
sing to a minimal amount at normal charging voltages.
Besides reducing gassing, the special chemistry greatly
reduces the possibility of overcharge damage.
Keep the battery in an upright position to prevent electro­
lyte leakage. Tipping the battery beyond a 45 degree angle
in any direction can allow a small amount of electrolyte to
leak out the vent hole.
Do not exceed this 45 degree angle when carrying or
installing the battery.
Evidence of electrolyte leakage does not always mean
the battery is defective.
CONTENTS (CONT.)

ELECTRICAL SYSTEM

BATTERY

have a "Check Engine" or "Service Engine Soon" lamp on
the instrument panel. Refer to the Fuel and Emissions Ser­
vice Manual for a detailed description of the lamp's opera­
tion and use as a diagnostic indicator.
Some vehicles sold in Canada may have variations in
electrical components. Refer to the appropriate Canadian
Service Manual Supplement.
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