Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Hydraulic pump is likely sucking air from the top connection or the filter area..any break in the suction side, lets air in and keeps the pump from sucking. It has lost prime. You can try to remove the upper connection, stuff the pump with grease from grease gun, reinstall the pipe and see if no with a better seal, it will pickup the oil. The system should not require bleeding!
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