(1) Working oil viscosity is too large or not injected into working oil.
(2) There are impurities in the working oil, so that the inlet valve is not tightly closed.
(3) The oil drain valve, unloading handle, and tension spring do not work; they are not in the lowest closed position or other debris is stuck.
(4) The position of the unloading handle and the drain valve are not adjusted very well.
(1) Change the working oil or inject the working oil according to the specified amount of oil.
(2) Remove impurities or replace working oil.
(3) Check that the tension spring is correct or not, and the unloading handle is adjusted to the lowest closed position to remove impurities.
(4) Re-adjust the position of the unloading lever nut.