The SUNTEC AP oil pump has a built-in solenoid which provides a two-mode pressure operation.
The gear-set draws oil from the tank through the built-in filter and transfers it to the pressure regulating valve.
The high pressure mode is obtained with the solenoid valve activated (ie. closed); activating this solenoid valve closes the by-pass channel to the return. Oil is then transferred to the nozzle line at the pressure given by the high pressure regulating valve.
The low pressure mode is obtained with the solenoid valve open (ie. non activated); the by-pass channel is open, the oil is supplied to the nozzle line via the by-pass hole and the low pressure adjustment is made by the screw on the solenoid tube.
It is preferable to set the high pressure given by the pump valve (with solenoid activated) before the low pressure, with solenoid non activated. Care should be taken not to overtighten the low pressure adjusting screw of the solenoid tube, as this may eliminate the low pressure range.
For two pipe installation, the by-pass plug fitted in the return port allows any oil not required at the nozzle to be dumped back to the tank. For one pipe installation, the by-pass plug must be removed and the return port plugged, oil which is not required at the nozzle is then returned back to the suction port in the gear set.
Bleeding is assured by the by-pass hole of the nozzle plug.
For the first start up, bleeding can be accelerated by loosening the plug of a pressure port.
Owing to the presence of the nozzle by-pass hole, the pump has no cut-off function; cut-off must be provided by an external solenoid valve.