General Description; Belt Driven Vacuum Pump; Gear Driven Vacuum Pump; Diagnosis Of Vacuum Pump - GMC G Service Manual

SUBJECT
General Description.................................................................................................................................................... 6H-1
Belt Driven Vacuum Pump......................................................................................................................................6H-1
Gear Driven Vacuum Pump.....................................................................................................................................6H-1
Diagnosis of Vacuum Pump.......................................................................................................................................6H-1
On-Vehicle Service...................................................................................................................................................... 6H-4
Belt Driven Pump Replacement..............................................................................................................................6H-4
Gear Driven Pump Replacement............................................................................................................................6H-5
Specifications.............................................................................................................................................................. 6H-6
Special Tools............................................................................................................................................................... 6H-7
The vacuum pump is mounted on diesel engines and
supplies power for operating emission controls, transmis­
sion modulators, cruise control, and air conditioning con­
trols. It may be belt driven or gear driven. Refer to
"Specifications" at the end of this section for model break­
down. The pump is a diaphragm pump which does not
require periodic maintenance.

BELT DRIVEN VACUUM PUMP

The belt driven model is bracket mounted at the right
front of the engine. It has a pulley attached which is driven

DIAGNOSIS OF VACUUM PUMP

Refer to figures 1 and 2 for diagnosis of the vacuum
pump.
SECTION 6H
VACUUM PUMPS
CONTENTS

GENERAL DESCRIPTION

by the generator belt. With the exception of the pulley, the
vacuum pump is replaced as an assembly.

GEAR DRIVEN VACUUM PUMP

The gear driven model is mounted at the top rear of the
engine. It is driven by a cam inside the drive assembly to
which it mounts. The drive housing assembly has a drive
gear on the lower end which meshes with the camshaft
gear in the engine. This drive gear causes the cam in the
drive housing to rotate. The drive gear also powers the
engine oil lubricating pump.
6H-1
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