Chrysler RAM TRUCK 2500 1994 Service Manual page 179

5 - 20 POWER BRAKE VACUUM PUMP (DIESEL MODELS)
POWER B R A K E VACUUM PUMP (DIESEL MODELS)
INDEX
page
General Information
20
Low Vacuum Warning Switch 20
Pump Adapter Replacement 23
Vacuum Pump Diagnosis
21
Vacuum Pump Operation
20
page
Vacuum Pump Replacement 22
Vacuum Pump Serviceability 20
Vacuum—Steering Pump Assembly Installation . . . 23
Vacuum—Steering Pump Assembly Removal 21
GENERAL INFORMATION
The power brake vacuum pump and the power
steering pump are combined into a single assembly
on diesel engine models (Fig. 1). Both pumps are op­
erated by a drive gear attached to the vacuum pump
shaft. The shaft gear is driven by the camshaft gear.
The vacuum pump is a constant displacement,
vane-type pump. Vacuum is generated by four vanes
mounted i n the pump rotor. The rotor is located i n
the pump housing and is pressed onto the pump
shaft.
The vacuum and steering pumps are operated by a
single drive gear pressed onto the vacuum pump
shaft. The drive gear is operated by the engine cam­
shaft gear.
The vacuum and power steering pump shafts are
connected by a coupling. Each pump shaft has an
adapter with drive lugs that engage i n 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.
The complete assembly must be removed in
order to service either pump. However, the
power steering pump can removed and serviced
separately when necessary.
VACUUM PUMP SERVICEABILITY
The vacuum pump is not a serviceable component.
I f diagnosis indicates a pump malfunction, the pump
must be 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.
I f the power steering pump requires service, simply
remove the assembly and separate the two pumps.
Refer to the pump removal and installation proce­
dures i n this section.
LOW VACUUM WARNING SWITCH
A vacuum switch is used to monitor output of the
vacuum pump. The switch is i n circuit with the
brake warning light.
VACUUM
GEAR ADAPTER
J9105-94
Fig. 1 Diesel Vacuum And Power 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 i n 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 i n
circuit with the red brake warning light.
The vacuum chamber is connected to the booster
check valve by a vacuum supply hose. A wire harness