A forklift must be inspected well and given a test run before purchasing it. This applies especially to trucks being acquired on line. It is important to detect possible issues with trucks obtained from businesses online.
Starting the engine from cold is a good idea. Note whether there is excessive smoke and the ease with which the engine turns over. This is especially vital with trucks which have IC engines.
Testing the performance of the truck in tough situations must be included in the test run. A qualified operator could drive the truck in reverse and forward, up the ramp.
You can check an IC engine truck yourself. On a clear area of floor, run the truck around for a few minutes while a trained driver tests the hydraulic functions. After that, examine the ground beneath for indications of fluid leakage. Even seemingly minor leaking can result in serious issues which would be expensive to repair later on.
A skilled individual should inspect the chains and masts. Check with and without a load that the mast operates smoothly. Watch for sticking or 'binding' of the mast. A warning indication is play in the mast channels or between the mast and fork carriage. Another is creeping down or creeping forward of the mast when loaded. These can be symptoms of problems with seals, ram or valve.
If the truck is used, the mast might have been changed at some time. Make certain that the mast and any fitted attachments adhere to the rating plate on a truck. Check that the sideshift is not sticking when loaded.
Looking closely at the thickness of the heel for damage or wear should be included in the inspection. The truck's manufacturer specifies minimum thickness. A loose fit can mean the carriage or hanger points are worn. Look for cracks on the arms at heels and mountings.