HYDRAULIC SYSTEM GRT8100 SERVICE MANUAL
2-26
Published 3/26/2018, Control # 596-05
Checking/Setting the Main Directional
Control Valve, Hoists, Lift, and Telescope
Pressures
1. Adjust the LS relief (see Figure 2-6) pressure setting
below the pressure setting of the piston pump cut-off
pressure by turning the LS relief counter-clockwise 2 full
turns.
2. With engine off, install a pressure check diagnostic quick
disconnect (9999101806) with gauge onto test nipple at
the GP gauge port on the main directional valve (see
Figure 2-6).
3. Start engine and idle. If the lift cylinder is installed, fully
retract it first. Slowly actuate the lift down function until
full stroke is achieved and hold. Slowly accelerate the
engine to full rpm. Turn the LS relief (see Figure 2-6)
clockwise to increase or counter-clockwise to decrease
so that a gauge reading of 4000 ±100 psi (276 bar
±7 bar) achieved.
4. Stop engine. Remove the diagnostic coupler.
5. If crane is equipped with a telescope extend relief on the
main directional valve (see Figure 2-6), turn relief screw
fully clockwise until completely seated. If crane is not
equipped with this relief, skip to step 6.
6. With engine off, install a pressure check diagnostic quick
disconnect with gauge onto the test nipple at the GP7
gauge port on the steer/swing brake/pilot supply
manifold (see Figure 2-8).
7. Start engine and let idle. Fully retract the telescope
cylinder if installed. Slowly actuate the telescope retract
function until full controller stroke is reached and hold.
Slowly accelerate the engine to full rpm. Turn the
telescope retract relief on the main directional valve (see
Figure 2-7) clockwise to increase or counter-clockwise
to decrease until a gauge pressure of 3250 ±50 psi
(224 ±4 bar) is achieved.
8. Stop engine. Remove the diagnostic coupler.
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