(1) the pump has air; this failure is generally installed when a new pump appears, when opening a new pump, you should first add oil to the pump, the pump bearing, plunger and cylinder from To lubricate.
Treatment method: When the pump is running, open the oil pump port, so that the pump air from the fuel tank discharge.
(2) the oil level of the tank is too low; suction pipe blockage makes the pump oil suction resistance caused by pump suction or into the oil pipe section of the leak, the pump inhaled the air.
Treatment: fill the oil as required; clean the filter, clear the intake pipe; check and tighten the oil into the tubing connection screw.
(3) pump and motor installed properly; that is to say the pump shaft and motor shaft concentricity is inconsistent, so that the pump bearing by the radial force to produce noise.
Remedy: Check the concentricity of the pump and motor installation.
(4) the viscosity of the hydraulic oil is too large; the pump's self-priming capacity is reduced and the volumetric efficiency is reduced.
Treatment: Select the appropriate viscosity of the hydraulic oil, if the oil temperature is too low should be heated.