A forklift should be inspected properly and given a test run before buying it. This applies specifically to trucks being purchased on line. It is important to find potential issues with trucks acquired from companies on line.
Starting the engine from cold is a great idea. Note whether there is excessive smoke and the ease with which the engine turns over. This is particularly vital with IC engine trucks.
Testing the performance of the truck in tough situations should be included in the test run. A trained operator can operate the truck in forward and reverse, up the ramp.
You can carry out your own inspection of an IC engine truck. On a clear part of floor, run the truck around for a few minutes while a skilled operator tests the hydraulic functions. After that, look at the ground underneath for signs of fluid leakage. Even seemingly minor leaking can lead to serious issues that will be really costly to repair later on.
A trained person must check the chains and masts. Check with and without a load that the mast works smoothly. Watch for sticking or 'binding' of the mast. A warning indication is play in the mast channels or between the fork carriage and mast. Another is creeping forward or creeping down of the mast when loaded. These can be symptoms of issues with ram, valve or seals.
If the truck is not new, the mast may have been changed at some time. Make certain that the mast and any fitted attachments follow the rating plate on a truck. Check that the sideshift is not sticking when loaded.
When inspecting the forks, look closely at the heel thickness for damage or wear. The manufacturer of the truck specifies minimum thickness. A loose fit might mean the hanger points or carriage are worn. Look for cracks on the arms at mountings and heels.