March 2008 "3072RT / 3772RT / 3772RT HD" Service & Parts Manual - ANSI Specifications
Page 4-10
Pump Adjustment
The Hydraulic Pump used in this model is a Variable Displacement, Pressure Compensated,
Piston type pump. Proper adjustment is critical for normal operation of the machine. The following
paragraphs will guide you through the various steps however, you must perform all steps, in their
listed sequence, in order to achieve proper adjustment and machine performance.
Main Relief and Standby Adjustments
1. Start engine and operate the unit for 15 minutes or until the hydraulic oil is warm.
2. Insert a 0 – 5000 PSI (0-345BAR) gauge onto the manifold pressure gauge port.
3. Remove the acorn nut from the Main Relief adjustment screw. Loosen the jam nut and
turn the screw counterclockwise 3 turns. Tighten the jam nut and install the acorn nut.
4. Remove the acorn nut from the Standby adjustment screw and loosen the jam nut. Turn
the screw clockwise 3 turns or until the needle on the gauge stops climbing. At this point
the gauge is reading full main relief pressure.
5. Access the Main Relief screw again and adjust it until the gauge settles at 2800 PSI
(193.5bar). Tighten the jam nut and install the acorn nut.
6. Check the gauge reading again to ensure the setting did not change.
7. Turn the Standby adjustment screw counterclockwise until the gauge reads 550 PSI
(38bar). Tighten the jamb nut and install the acorn nut.
8. Check the gauge reading again to ensure the setting did not change.
Pump Displacement Adjustment
This adjustment is set at the factory and should not be tampered with. The Displacement
adjustment controls the maximum amount of oil flow that the pump will produce per revolution.
Excessive flow will result in severe engine loading and stalling. Reduced flow will result in slower
functions with no engine loading. If you suspect that the sitting is incorrect, please call MEC
Product Support at (800) 387-4575 for assistance.
Main Relief
See Pump Adjustment Procedure.
Stand-By Pressure
See Pump Adjustment Procedure.
Lift Relief (RV1)
The Lift Relief valve is located on the left-side, center of the valve manifold. It will be necessary to
remove the cap from the relief valve if adjustment is necessary. REMOVING THE CAP WHILE
THE ENGINE IS RUNNING WILL RESULT IN OIL LEAKAGE.
To check Lift Relief valve setting, park the machine on a firm level surface free from overhead
obstructions. Using the lift switch on the lower panel, elevate the platform to full elevation. While
maintaining the lift command, record the reading on the gauge.
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