Erratic Pump Movement

To avoid serious injury follow all warnings and instructions in the manual. Wear appropriate personal protective equipment.

  • Feed pump pressure is too low. Adjust pressure to maintain 100 psi (0.7 MPa, 7 bar) minimum.
  • Fluid is too thick. Consult your material supplier for the recommended fluid temperature to maintain a viscosity of 250-1500 centipoise
  1. Check the functionality of each proximity switch.
    • Remove the front cover.
    • With the motor powered off, confirm that the indicating light son the body of each proximity switch turns on when a metallic item, such as the shaft of a screwdriver, is placed on the face of each switch.
    • If the indicating lights turn on, the proximity switches and switch wiring are likely operating correctly; proceed to step 2. If the indicating lights do not turn on, proceed to step 6.
  2. Confirm the proximity switches, switch bracket, and switching plate are firmly mounted and not damaged.
  3. Check distance between the proximity switches and the switching plate.
    • Park the pump.
    • Confirm that the proximity switch nearest the A-side of the pump is backed out 0.5 to 1.5 turns from being in contact with the switching plate.
    • Disconnect the cable from the proximity switch nearest the B-side of the pump. Operate the pump until the switching plate is located above the B-side proximity switch, then turn off the motor/pump. 
    • Confirm that the proximity switch nearest the B-side of the pump is backed out 0.5 to 1.5 turns from being in contact with the switching plate. 
    • Reconnect the cable to the B-side proximity switch.
  4. Check functionality of the directional valve.
    • Inspect wiring inside the cover of the directional valve. See Electrical Schematics, in manual.
    • During operation, the direction indicator lights on the directional valve body should switch on based on the valve that is open.
    • Turn on the motor and stall the pumps at the lowest pressure setting (compensator knob turned fully counter-clockwise). The pump will travel in either the A or B direction until the pressure setting is reached.
    • Identify the solenoid that is operating by viewing the direction indicator lights on the cover of the directional valve. Measure voltage across the associated terminals to determine if proper voltage is reaching the valve (approximately 200 to 240 VAC). See Electrical Schematics, in manual, and the Pump Position Table to identify the proper terminals to measure across.
    • Trigger each proximity switch with the shaft of a screwdriver, confirming each solenoid within the directional valve operations as described in the Pump Position Table.
    • If one or both sides are not operating properly, according to the Pump Position Table, first reconfirm wiring to directional valve per Electrical Schematics, in manual, then replace directional valve.
  5. If you have determined that the cause is none of the previous possible causes, check for a loose piston packing retaining bolt. This causes the piston to contact the inner face of the pump inlet flange before the switching plate activates the proximity switch. Shut down the unit and disassemble the appropriate pump for repair.
  6. Following step one, if the proximity switch indicating lights do not light:
    • Check for loose or faulty proximity switch cable or connections. Confirm the connections to the proximity switches are tight and internally free from oil and other contaminates.
    • Swap the cables to the proximity switches to see if the problem follows the switch or is in the cable. Replace either the failed switch or the cable.