A forklift should be inspected correctly and given a test run prior to buying it. This applies specifically to trucks being purchased on-line. It is essential to find possible problems with trucks obtained from businesses on the Internet.
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 particularly vital with IC engine trucks.
The test run must include a check of the truck's performance in challenging situations. A qualified driver can drive the truck in reverse and forward, up the ramp.
You could check an IC engine truck yourself. On a clear area of floor, run the truck around for several minutes while a qualified operator tests the hydraulic functions. Then, look at the ground underneath for indications of fluid leakage. Even seemingly insignificant leaking can lead to serious issues which would be really costly to fix later on.
A trained individual must inspect the chains and masts. Check with and without a load that the mast works well. Watch for 'binding' or sticking of the mast. A warning sign is play in the mast channels or between the mast and fork carriage. One more is creeping forward or creeping down of the mast when loaded. These could be symptoms of issues with ram, valve or seals.
If the truck is not new, the mast might have been changed at some time. Make sure that the mast and any fitted attachments follow the rating plate on a truck. Check that the sideshift is not sticking when loaded.
When checking the forks, look closely at the heel thickness for wear or damage. The manufacturer of the truck specifies minimum thickness. A loose fit can mean the carriage or hanger points are worn. Watch for cracks on the arms at mountings and heels.