Chrysler 1991 Service Manual Supplement page 8

• BRAKES 5 - 1
B R A K E S
DIESEL VACUUM PUMP
INSTALLING VACUUM-STEERING PUMP
ASSEMBLY
LOW VACUUM WARNING SWITCH
PUMP ADAPTER REPLACEMENT
REMOVING VACUUM-STEERING PUMP
ASSEMBLY
C O N T E N T S
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VACUUM PUMP DIAGNOSIS . . .
VACUUM PUMP OPERATION . .
VACUUM PUMP REPLACEMENT
VACUUM PUMP SERVICEABILITY
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DIESEL VACUUM PUMP
A new design power brake vacuum pump is used
on 1991-1/2 AD models with the Cummins turbo die-
sel engine. However, the new vacuum pump is still
combined with the power steering pump into a single
assembly (Fig. 1).
The new vacuum pump is a constant displacement,
vane-type pump. Vacuum is generated by four vanes
mounted in the pump rotor. The rotor is located in
the pump housing and is pressed onto the pump
shaft.
The vacuum and steering pumps are both operated
by a single drive gear pressed onto the vacuum pump
shaft. The drive gear is operated by . the camshaft
gear.
The vacuum and power steering pump shafts are
connected by a coupling. Each pump shaft has an
adapter with drive lugs that engage in the coupling.
The vacuum pump rotating components are lubri-
cated by engine oil. Lubricating oil is supplied to the
pump through an oil line at' the underside of the
pump housing.
VACUUM PUMP SERVICEABILITY
The vacuum pump is not a serviceable component.
If diagnosis indicates a pump malfunction, the pump
must be removed and replaced as an assembly. Do
not disassemble or attempt to repair the pump.
The combined vacuum and steering pump assembly
must be removed for access to either pump. However,
the vacuum pump can be removed without having to
disassemble the power steering pump.
If the power steering pump requires service, simply
remove the assembly and separate the two pumps.
Refer to the pump removal and installation proce-
dures in this section.
LOW VACUUM WARNING SWITCH
A vacuum switch is used to monitor output of the
vacuum pump. The switch is in circuit with the
brake warning light.
VACUUM
GEAR ADAPTER
J9105-94
Fig. 1 Vacuum And Steering Pump Assembly
A vacuum hose connects the switch to the power
brake booster. A wire harness connects the switch to
the brake warning light.
The switch is mounted on the driver side inner
fender panel just below the hood hinge (Fig. 2).
VACUUM PUMP OPERATION
Vacuum pump output is transmitted to the power
brake booster through a supply hose. The hose is con-
nected to an outlet port on the pump housing and to
the check valve in the power brake booster.
Pump output ranges from a minimum of 8.5 to 25
inches vacuum.
The pump rotor and vanes are rotated by the pump
drive gear. The drive gear is operated by the cam-
shaft gear.
Booster vacuum level is monitored by a warning
switch (Fig. 2). The switch consists of a vacuum
chamber that measures vacuum level and a sensor in
circuit with the brake warning light.