1. Pump off.

2. Flow interrupted/obstructed.

3. Leak.

4. Air trapped in pump head. (Revealed by pressure fluctuations.)

1. Start pump.

2. Check mobile phase level in reservoir(s). Check flow throughout system. Examine sample loop for obstruction or air lock. Make sure mobile phase components are miscible and mobile phase is properly degassed.

3. Check system for loose fittings. Check pump for leaks, salt buildup, unusual noises. Change pump seals if necessary.

4. Disconnect tubing at guard column (if present) or analytical column inlet. Check for flow. Purge pump at high flow rate (e.g., 5-10 mL/min.), prime system if necessary. (Prime each pump head separately.) If system has check valve, loosen valve to allow air to escape. If problem persists, flush system with 100% methanol or isopropanol. If problem still persists, contact system manufacturer.