178 Troubleshooting
Pump
The pump is operated by a control switch located on the control panel. When it is engaged, the switch
turns green.
Three conditions must be met for the pump to engage and the switch to turn green:
Air pressure must be at approximately 70 psi
Engine speed must be lower than 900 rpm
Emergency S
TOP button (red) must be pulled out
Air pressure condition is verified by a pressure switch, and engine speed, by the transmission
ECU.
If the pump does not engage when the pump switch is turned on, it may be related to a voltage supply
problem in the pump circuitry.
The following test will help resolve pump-related problems. Prior to the test, ensure that all these
conditions are met:
Parking brake applied
Engine is running (idle speed)
Transmission in “Neutral”
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TOP button(s) pulled out
Pump (
PTO) switch ON
NOTE: Neither the engine throttle nor the transmission not being in Neutral will affect pump
operation once the pump is engaged.
Pump Cavitation
Cavitation is defined as the formation of air pockets in a moving fluid. Air in the hydraulic oil causes
excessive wear and noise. Make sure to prime the pump properly before installing it or after flushing
the hydraulic system (refer to “Priming a New Pump” on page 136). When the pump is properly
primed, cavitation disappears after a short time because air is returning to the hydraulic tank.
If the pump is still generating unusual noise after performing the priming procedure, you will have to
bleed the hydraulic system.
To do so:
1. Apply all safety measures to ensure safety around the vehicle at all times.
2. Connect a 0–4000 psi gauge to the main valve to ensure that no pressure has built up in the
system.
3. Apply the parking brake and start the engine.
4. Engage the hydraulic pump (pump/PTO switch “ON”).
5. Place a pan or a bucket under the plug located on the main control valve output section and
slowly loosen the plug.
A mixture of oil and air will come out. Keep bleeding the oil until the pump noise stops.
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