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| Illustration 1 | g00394281 |
Location of Steering Metering Pump | |
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| Illustration 2 | g00282859 |
Steering Metering Pump NEUTRAL position (1) Inner spool (2) Drain outlet to tank (3) Left turn port (4) Outer sleeve (5) Right turn port (6) Inlet (7) Passage (8) Stator (9) Rotor (10) Passage (11) Drive (12) Pin (13) Centering springs (A) Control section (B) Metering section | |
The steering metering pump is located on the base of the steering column under a cover at the front of the cab. The resilient mounting of the metering pump will prevent vibration damage and noise.
The steering metering pump is made up of the following two sections:
- Control section (A)
- Metering section (B)
The two sections are connected by hydraulics and by mechanics.
The steering solenoid and relief valve will direct oil to inlet (6) and into the control section (A) . When the steering wheel is turned, control section (A) sends oil to metering section (B) . Metering section (B) produces a specific amount of oil flow. Metered oil from metering section (B) is then directed by control section (A) to either left turn port (3) or right turn port (5) . This oil is then directed to the steering cylinders in order to turn the machine. As the steering wheel is turned faster, there is an increase in the flow of oil. The steering cylinders will move farther with increased speed.
Oil Flow
Control section (A) of the steering metering pump is a closed center type. When the steering wheel is in the NO STEER position, there is no alignment between the holes in sleeve (4) and the passages in spool (1) . However, a small amount of pump oil from inlet (6) is allowed to flow through the center position of the steering metering pump. This small amount of oil flow (thermal purge) keeps the steering metering pump full. This will improve response time to the steering demands. The oil flow also helps keep the oil lines to the steering metering pump warmed during cold weather operations.
Right Turn
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| Illustration 3 | g00287150 |
Steering Metering Pump Right Turn (1) Inner spool (4) Outer sleeve (5) Right turn port (6) Inlet (7) Passage (8) Stator (9) Rotor (10) Passage (11) Drive (12) Pin (13) Centering springs (A) Control section (B) Metering section | |
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| Illustration 4 | g00282755 |
Spool and sleeve (1) Inner spool (4) Outer sleeve (14) Holes for pin (12) (15) Small holes for oil flow (16) Grooves for oil flow (17) Slots for centering springs | |
When the steering wheel is turned clockwise, spool (1) , pin (12) and drive (11) start to turn. Sleeve (4) did not start to turn at the same time. This is the result of the diameter of the holes (14) in sleeve (4) that are slightly larger than the diameter of pin (12) . Spool (1) will turn inside sleeve (4) enough to put the holes (15) in sleeve (4) in line with the grooves (16) in spool (1) . The oil path in the center position of the steering metering pump is blocked by the rotation of spool (1) and sleeve (4) .
Pump oil from inlet (6) goes through small holes (15) in sleeve (4) into grooves (16) in spool (1) . The oil in grooves (16) goes out through other small holes (15) in sleeve (4) and into passage (10) . Oil flows through passage (10) into metering section (B) . Then, the oil is directed into a space between stator (8) and rotor (9) .
Rotor (9) is splined to drive (11) . As drive (11) turns, rotor (9) pumps oil through passage (7) . The metered oil flows back into sleeve (4) through small holes (15) and into other grooves (16) in spool (1) . This oil then exits sleeve (4) through small holes (15) . Then, the oil flows into right turn port (5) . Oil from port (5) flows to the steering cylinders in order to turn the machine.
When the steering wheel is not turned, spool (1) , pin (12) , drive (11) and rotor (9) will not turn. Centering springs (13) will bring spool (1) and sleeve (4) back to the NEUTRAL position. Small holes (15) in sleeve (4) are not in alignment with grooves (16) in spool (1) . Metered oil to right turn port (5) stops. This causes the wheels to stay in the current position.
Left Turn
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| Illustration 5 | g00287151 |
Steering Metering Pump Left Turn (1) Inner spool (3) Left turn port (4) Outer sleeve (6) Inlet (7) Passage (8) Stator (9) Rotor (10) Passage (11) Drive (12) Pin (13) Centering springs (A) Control section (B) Metering section | |
The operation is in the opposite direction. When the steering wheel is turned counterclockwise for a left hand turn, spool (1) , pin (12) and drive (11) start to turn. Oil comes in inlet (6) . Since spool (1) and sleeve (4) are turned, a different set of holes and grooves will line up. Oil flows through spool (1) and sleeve (4) into passage (7) and metering section (B) . Metered oil flows through passage (10) , spool (1) and sleeve (4) , and exits left turn port (3) . Oil flows to the steering cylinders in order to turn the machine.
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| Illustration 6 | g00298198 |
(11) Drive (12) Pin (18) Timing mark (19) Valleys of gerotor star (A) Reference line (B) Reference line (C) Reference line | |
If the steering metering pump is disassembled, assemble the steering metering pump properly. Failure to assemble the steering metering pump properly will result in erratic steering. In order to assemble the steering metering pump correctly, use the timing mark (18) on drive (11) . The timing mark (18) on drive (11) must be on the parallel line between any two valleys of the gerotor star (19) .
Note: Reference lines (A) , (B) , and (C) are parallel.