A sand and gravel operation reported that a Lovol FL958H wheel loader's steering would "hesitate" (pause before turning) and the lift cylinder would not raise the boom when the engine was at low idle.
The technician diagnosed the "Steering Priority System." The system uses a "Priority Flow Control Valve" that directs oil to the steering circuit first. Excess flow is sent to the implement (lift) circuit. He checked the "Priority Spring" inside the valve housing. The spring was broken into three pieces. The broken spring prevented the spool from moving to the "Steering Priority" position. This caused the oil to flow to the lift circuit instead of steering, explaining why steering was slow.
The "No Lift" issue at low idle was a separate "Suction Side" problem. He inspected the "Hydraulic Tank Suction Line." The hose was old and had collapsed internally (the wire reinforcement was rusted and bent). The collapsed hose restricted the flow of oil to the pump. At high idle, the pump could overcome the restriction, but at low idle, the flow was insufficient to generate pressure for the lift circuit.
The repair involved replacing the priority valve spring and the suction hose. The hydraulic tank was also checked for sludge (due to the rusted hose). The tank was cleaned, and the oil was replaced. After reassembly, the steering response was instant, and the boom lifted smoothly even at low idle.
