STEERIN G
9 -1 7
Fig. 23—Pump Components
the inner cam surface of the pump ring, moving outward
and inward twice during each revolution. This results in
a complete pumping cycle every 180 degrees of rotation
(Fig. 23). Oil is moved in the spaces between the vanes.
As the vane tips move outward, oil is sucked into the
intervane spaces through four suction ports in the
pressure and thrust plates. The pressure of the oil is
raised, and the oil is discharged from the pump ring, as
the vane tips move inward. High pressure oil discharges
into cavity 1 (Figs. 25, 26 and 27), through two open
ports in the pressure plate, and through two blind ports
in the thrust plate, which are connected to cavity 1 by the
cross-over holes in the ring. A portion of this oil is
circulated through the central port system in the pressure
plate, forcing the vanes to follow the cam surface of the
ring. The ring-rotor leakage oil (12) is used for bushing
lubrication and then bled to the reservoir.
SLOW CORNERING (Fig. 25)
During slow cornering maneuvers, the oil pressure
required will usually not exceed 400 p.s.i. The speed of
the pump is not high enough to require internal
bypassing of oil, therefore, the pump by-pass port to (5)
remains closed. The high pressure discharge oil (7) is
slightly lower in pressure than the internal high pressure
oil (1). The drop in pressure occurs as oil flows through
the flow control orifice (2). This lower pressure is
communicated to the bottom end of the pump control
valve (9) via orifice (11) and passage (8), resulting in a
pressure unbalance on the valve itself. The flow control
valve moves away from the discharge fitting, but due to
the force of the flow control spring (10) the valve
remains closed to the bypass hole (5). The oil pressure
does not build up high enough to cause the pressure
relief valve to actuate, because the oil pumped through
the steering gear is allowed to recirculate through the
entire system.
MODERATE TO HIGH SPEED OPERATION
(Fig. 26)
When operating at moderate to high speed, it is
desirable to limit the temperature rise of the oil. This is
done by flow controlling. The control valve in the
steering gear is an open center rotary valve. When this
valve is in the straight ahead position, oil flows from the
pump through the open center valve and back to the
pump reservoir without traveling through the power
cylinder. When this flow exceeds the predetermined
system requirements, oil is bypassed within the pump.
This is accomplished by the pressure drop which occurs
across the flow control orifice (2). The pressure is reduced
at the bottom of the flow control valve (9) via orifice (11)
and passage (8). The pressure unbalance on the valve is
sufficient to overcome the force of the spring (10),
allowing the valve to open the bypass hole (5), and
diverting oil into the intake chamber (6). Supercharging
of the intake chamber occurs under these conditions. Oil
at high velocity discharging past the valve into the intake
chamber picks up make-up oil at hole (4) from the
reservoir on the jet pump principle. By reduction of
velocity, velocity energy is converted into supercharge
pressure in cavity (6). During this straight ahead driving
condition, the discharge pressure should not exceed 100
p.s.i.
CORNERING AGAINST WHEEL STOPS (Fig.
27)
When the steering gear control valve is actuated in either
direction to the point of cut-off, the flow of oil from the
pump is blocked. This condition occurs when the front
wheels meet the wheel stop, or when the wheel
movement is otherwise blocked by a curb or deep sand
or mud. The pump is equipped with a pressure relief
valve. The relief valve is contained inside the flow
control plunger (13). When the pressure exceeds a
predetermined pressure, (greater than maximum system
requirements) the pressure relief ball (14) opens,
allowing a small amount of oil to flow into the bypass
hole (5). This flow of oil passing through the pressure
relief orifice (11) causes a pressure drop and resulting
lower pressure on the bottom end of the control valve
(9).
The pressure unbalance then causes the valve to
compress the spring (10) allowing the major portion of
the oil to bypass into the intake chamber (from 3 to 6) in
the same manner as is accomplished by flow controlling.
Relief pressures are usually between 1200 and 1300 p.s.i.
depending on the vehicle requirements.
LIGHT DUTY TRUCK SERVICE MANUAL
Summary of Contents for Light Duty Truck 1973
Page 1: ......
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Page 53: ...HEATER AND AIR CONDITIONING 1A 27 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 115: ...LIGHT DUTY TRUCK SERVICE M A N U A L HEATER AND AIR CONDITIONING 1A 89...
Page 123: ...BODY 1B 3 Fig 6 Typical 06 Van LIGHT DUTY TRUCK SERVICE MANUAL...
Page 149: ...BODY 1B 29 Fig 84 Body Mounting 06 Fig 85 Body Mounting 14 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 171: ...LIGHT DUTY TRUCK SERVICE M A N U A L Fig 2 Frame Horizontal Checking Typical FRAME 2 3...
Page 173: ...LIGHT DUTY TRUCK SERVICE M A N U A L Fig 4 10 30 Series Truck Frame FRAME 2 5...
Page 174: ...2 6 FRAME LIGHT DUTY TRUCK SERVICE MANUAL Fig 5 Underbody Reference Points G Van...
Page 185: ...FRONT SUSPENSION 3 11 Fig 16 Toe out on Turns LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 351: ...ENGINE 6 15 Fig ID Sectional View of Eight Cylinder Engine LIGHT DUTY TRUCK SERVICE MANUAL...
Page 375: ...EN G IN E 6 39 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 376: ...6 4 0 ENGINE LIGHT DUTY TRUCK SERVICE MANUAL...
Page 377: ...ENG IN E 6 41 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 378: ...LIGHT DUTY TRUCK SERVICE MANUAL Fig 37L K Series Engine Front Mount 6 42 ENG INE...
Page 400: ...6 6 4 ENG INE LIGHT DUTY TRUCK SERVICE MANUAL...
Page 401: ...ENG IN E 6 65 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 402: ...6 6 6 ENGINE LIGHT DUTY TRUCK SERVICE MANUAL...
Page 403: ...E NG IN E 6 67 Fig 36V C Series Engine Mounts LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 423: ...EN G IN E C OOLING 6K 13 Fig 16 Overheating Chart LIGHT DUTY TRUCK SERVICE MANUAL...
Page 424: ...6 K 1 4 ENG INE COOLING Fig 17 Coolant Loss Chart LIGHT DUTY TRUCK SERVICE MANUAL...
Page 456: ...6M 32 ENGINE FUEL Fig K15 Accelerator Controls G Van L 6 LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 512: ...Fig 18e Vacuum Advance Diagram V8 Engine...
Page 516: ...6 T 2 4 E M IS S IO N CONTROL SYSTEMS LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 593: ...CLUTCHES MANUAL TRANSMISSIONS 7M 3 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 598: ...7M 8 CLUTCHES MANUAL TRANSMISSIONS LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 743: ...FUEL TANKS AND EXHAUST 8 13 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 744: ...8 14 FUEL TANKS AND EXHAUST LIGHT DUTY TRUCK SERVICE MANUAL...
Page 760: ...8 30 FUEL TANKS AND EXHAUST Fig 40 Exhaust Pipe P Models LIGHT DUTY TRUCK SERVICE MANUAL...
Page 761: ...FUEL TANKS AND EXHAUST 8 31 LIGHT DUTY TRUCK SERVICE MANUAL...
Page 763: ...FUEL TANKS AND EXHAUST 8 33 LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 832: ...LIGHT DUTY TRUCK SERVICE MANUAL Fig 106 Power Steering Pump Mounting Typical 9 66 STEERING...
Page 833: ...PUMP ASSEMBLY STEERING GEAR TYPICAL SMALL V8 TYPICAL LARGE V8 STEERING 9 67...
Page 861: ...STEERING 9 95 Fig 134 Power Steering Pump Leakage LIGHT DUTY TRUCK SERVICE MANUAL...
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Page 886: ...11 10 CHASSIS SHEET METAL LIGHT DUTY TRUCK SERVICE MANUAL...
Page 891: ...ELECTRICAL BODY AND CHASSIS 12 5 LIGHT DUTY TRUCK SERVICE MANUAL...
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