Kenett power unit service tips

06/01/2004

I. Problem: motor runs and makes a smooth hum with the pressure bleed valve closed.

  1. Lower the pressure to "0" psi slowly to prevent excessive foaming of the fluid. When the pressure is "0", check the fluid level in the top sight glass, and make sure the level is normal. With the fluid level at normal, close the pressure bleed valve. Close 0 8M to run the motor and watch the hydraulic pressure gauge. The pressure will rise slowly, pause, then take a large swing. When it makes this large swing, this indicates the precharge pressure. The precharge pressure is listed on the data plate riveted to the cabinet door. If the precharge pressure is too low, you could drop the fluid level below the suction filter before reaching normal pressure. The pump would then pick up air and lose prime, so be sure the precharge pressure is normal for this hydraulic power unit. To correct the precharge pressure, consult the operator instruction book.
  2. With the pressure bleed valve still open, start the motor, and let it run for two or three minutes to expel air from the system.
  3. Close the pressure bleed valve, and if the pressure now builds up to normal, the system was airbound. If the pump does not build up pressure, it could be a separated coupling, a stuck or fouled check valve, or a problem in the pilot valve, and/or ball valve, trash in the check valve, or sticking pump suction valve.
  4. There are three models of the Kenett hydraulic pump. The first model had a 90 degree intake cap and blank plates bolted on two of the three sides. The second had a straight intake cap, otherwise it was the same as the first model. The third model had a round pump housing and the pressure port was located on the left side with the pump element in the front.

II. Solutions: to localize the problem, you will need to lower the reservoir tank.

  1. Remove the small tube clamp on the right side of the reservoir tank.
  2. Remove the support angle from the bottom side of the reservoir tank.
  3. Support the reservoir tank with blocks, or hydraulic jack, and prepare to lower the tank to the floor of the operator cabinet.
  4. Remove the reservoir mounting bolts, start with two bolts at rear. These are 5/16" allen head. A hex key wrench, mounted in a socket, a 3/8" ratchet and extension and extension is ideal for use on these bolts.
  5. Lower the reservoir tank to the cabinet floor. A six foot long 2" x 4' wooden lever works very well for lowering the tank. Be careful not to tear the reservoir gasket.
  6. The motor to pump coupling, the pump, the suction lines, return line, and bottom of the manifold assembly are not visible. Visually check the motor to pump coupling.
  7. The coupling should be fully meshed with about 1/16" separation of the metal coupling halves. The rubber spider should not be torn or damaged. If the coupling halves have slipped on either the pump or motor, they should be removed and a new screw added 90 degrees from the original set screw. Use a #7 tap drill, 1/4"- 20x 1/4" long set screw. Use loc Quick primer on the set screw threads, coupling and shafts. After the coupling is installed on the motor shaft, prick punch the key slot, so the key cannot move up the slot. The motor mounting bolts, are 3/16" allen screws.
  8. Removing the power pump. Remove the main return line and hand pump suction line for convenience. Remove the power pump pressure line. Remove pump mounting bolts, while supporting the pump unit in your hand. CAUTION: Handle the filters with care, they are made of paper composition and may be damaged easily. If damaged, replace these filters, as very small pieces can prevent the seating of the check valves.
  9. Removing the power pump motor. Pull the 0 8M knife switch and fuses. Disconnect the wires in the motor wire box (11/32 wrench). Remove item 666, motor mounting bolts, which may be either 5/16" or 1/4" allen screw. Lift motor from mounting, being careful not to let the rubber spider in the coupling fall into reservoir.

III. Testing the power pump for leaks.

  1. With the power pump removed, remove the filter from suction line. Plug the pump discharge port with a .375NPT pipe plug. Apply five to ten psi maximum pressure to the power pump suction line, item 661. A bi-cycle air pump will do the job. Check each fitting, bolts flanges, tube connectors, pump element, shaft seal, and pump housing for leaks. The hydraulic fluid is a food leak detector, and the pump may be completely submerged in the fluid without contamination.
  2. There are gaskets and "O" rings under the pump element and on the older models of the pump housing. There were two blank plates with gaskets and "O" rings. If tightening the screws on these items does not stop them from leaking, you should carefully inspect the "O" ring and gasket. Be careful not to lose the small "O" ring. These "O" rings sometimes stick to the paper gasket.
  3. If the intake cap leaks, check the "O" ring and the steel seal ring. The newer model pump has a straight intake cap and does not use the adapter or the seal ring. If the seal ring should leak, you can obtain an "O" ring and install it under the seal ring. Lubricate the "O" with either hydraulic fluid or clean petroleum jelly before replacing the intake cap. The old style intake cap is interchangeable with the new one. CAUTION: Do not use Teflon tape on any of the threaded fittings of the hydraulic system. The tape has a tendency to extrude into the system and foul the check valves.