1. Motor Does Not Run / Pump Does Not Start

• Power failure or circuit trip: No power from the outlet, tripped breaker, blown fuse, or damaged power cable → Use a multimeter to check voltage, reset the breaker, replace the fuse, and inspect the cable.

• Faulty switch or contactor: Start/stop switch, relay, or AC contactor contacts are burnt or damaged → Disconnect power, check continuity, and replace faulty components.

• Motor failure: Motor only makes a "humming" sound but does not rotate = seized bearings, burnt windings, or worn carbon brushes (common on DC hydraulic pumps) → Inspect the motor and repair or replace if necessary.

• Thermal protection activated: Pump body or hydraulic oil temperature is too high (typically protection activates above 60°C) → Stop operation and allow the system to cool to normal temperature before restarting.

• Incorrect rotation direction (three-phase pumps): Pressure cannot build up or no oil output → Swap any two phase wires to reverse motor rotation.
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2. Motor Runs but Pressure Cannot Build / Low Flow Output

Troubleshooting sequence: Check the valve first, then the pump, then internal leakage.

Low oil level or clogged suction filter: Oil level is below the suction port or the filter screen is blocked → Add hydraulic oil to the correct level mark and clean or replace the filter element.

Air entering the suction line (cavitation): Cracked suction hose, loose fittings, or leaking seals → Tighten connections, replace damaged hoses, and bleed air from the system.

Relief valve / safety valve malfunction: Pressure adjustment screw is loose, valve spool is stuck in the relief position, or spring is broken → Remove and clean the relief valve, readjust pressure settings, and replace damaged parts if required.

Internal pump wear and leakage: Excessive clearance in gear pump side plates or gear tips, scratched piston pump valve plate, or check valve unable to seal properly → Test no-load pressure. Excessive internal leakage requires pump disassembly and component replacement.

Insufficient motor speed: Low supply voltage (especially when using long extension cables with 220V pumps) → Measure voltage under no-load conditions, use thicker cables, or connect directly to the power supply.

Incorrect oil type or contaminated hydraulic oil: Oil is too thick for cold weather operation, or oil is emulsified/contains air → Replace with the correct grade of anti-wear hydraulic oil (commonly ISO VG 46 or ISO VG 32).

3. Excessive Noise / Noticeable Vibration

• Air trapped in the hydraulic system: Most common after initial installation or oil replacement, usually accompanied by a "gurgling" sound → Loosen the bleed screw and jog the motor repeatedly under no-load conditions to circulate oil and remove trapped air.

• Poor suction conditions: Blocked filter, low oil level, undersized suction line, or oil with excessive viscosity → Clean the filter, increase suction line diameter, or replace the hydraulic oil.

• Mechanical wear: Damaged bearings, worn gears/vanes/pistons, misaligned coupling (shaft alignment error >0.1mm) → Replace bearings, correct alignment, and tighten mounting bolts.

• Cavitation noise: A continuous high-pitched noise lasting more than 30 seconds indicates the pump is drawing air or starving for oil → Stop operation immediately and inspect the suction-side seals, connections, and oil level.