Why do I detect no peaks or only very small peaks?

Regular:

Solution: Turn on lamp. b.) Loose/broken wire between detector and Computer.
Solution: Check electrical connections. c.) No mobile phase flow.
Solution: Start pump. 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. Check system for loose fittings. Check pump for leaks, salt buildup, unusual noises. Change pump seals if necessary. Disconnect tubing at column inlet. Check for flow. Purge pump at high flow rate (e.g. 5 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. d.) No sample/deteriorated sample.
Solution: Be sure automatic sampler vials have sufficient liquid and injector valve works well. Evaluate system performance with fresh standard to confirm sample as source of problem. e.) Settings too high on detector/Software.
Solution: Check attenuation or gain settings.