Adjusting The Automatic Throttle Control; Automatic Throttle Adjustment - Husqvarna PP 418 Operator's Manual

ADJUSTING THE AUTOMATIC THROTTLE
GENERAL DESCRIPTION
The AUTOMATIC THROTTLE function is triggered by an
adjustable pressure switch located on the hydraulic manifold.
Throttle Control
Pressure Switch
When the fl ow selector is set to (for example) 40 liters (10 gal),
that amount of oil will circulate through the hoses and through
the tool and back to the tank.
The circulation of the oil through the hoses creates a small
pressure (known as "back pressure") at the pressure switch.
The back pressure in the system can vary for many reasons
such as;
- Cold hydraulic oil
- The length of the hoses – a longer hose
creates more back pressure.
- The valve in the hydraulic tool can have a
high restriction.
In some applications the hydraulic system restriction may be
too low. This will cause the engine to remain at idle speed
even after the tool is engaged and full power is required.
When a trigger is activated at the tool, the oil pressure quickly
rises to in excess 50 bar (700 psi). This normally triggers the
AUTOMATIC THROTTLE control to increase the throttle to
"FULL". It is desirable that the engine engages to full throttle
immediately when the tool is activated.
On the PP 418 the threshold pressure at which the
throttle reacts can be adjusted to reach a desired function for a
specifi c tool and condition.
Step 1
Hook up the hoses and tool to be used.
Step 2
Turn the AUTOMATIC THROTTLE switch to the ON position.
Start the engine and let it idle for 1 minute. The engine will
now idle at 1900 RPM.
Step 3
Turn the FLOW SELECTOR to the proper setting for the tool.
Pressure
Note: If the oil is cold the back pressure in the system can
Relief Valve
trigger the full throttle function.
Step 4
Let the hydraulic oil warm up for one or two minutes. It is now
OK to start the work. The hydraulic oil will reach a stabilized
operational temperature in approximately 5 to 10 minutes.
Step 5
If the machine has been operated for 10 minutes and the
AUTOMATIC THROTTLE function is not working correctly
the pressure threshold value between the idle and full throttle
function can be adjusted.
NOTICE:
The Throttle Control Pressure Switch setting has NO impact
on the relief valve setting (= maximum system pressure). It is
strictly sensing the system pressure to signal the controller to
operate the engine at Idle or Full Throttle.
DO NOT adjust the pressure relief valve.
Scenario 1.
With the Automatic throttle switch in the ON position, the
engine will stay at FULL THROTTLE even when the hydraulic
oil is hot.
Adjustment
Scenario 2.
The engine will remain at IDLE SPEED when the tool is
engaged. It might work OK when the oil is cold.
Adjustment
13
ADJUSTMENT
Use an 8 mm or 5/16" hex
key to adjust the throttle
threshold pressure
Turn the Adjustment Screw -
Clockwise in 1/8 turn increments
until proper function is achieved.
Turn the Adjustment Screw -
Counter Clockwise in 1/8 turn increments
until proper function is achieved.