Floor jacks are pretty small objects that are really strong and sturdy as well. If there is some sort of heavy weight item that you need to work on, but you need to access its bottom, then a floor jack is what you need. It will lift the heavy weight items for you while you can work at the bottom of it.
Floor jacks are not at all complicated to use, just a bit of cranking and pumping is all that you need to do in order to lift those heavy objects but the major drawback to these floor jacks is that they are very easily damaged. You can click to read more about fixing floor jacks that will not lift.
Although floor jacks are very capable of lifting heavy objects, but there is a limit to it as well. Each floor jack comes with a weight lifting capacity, if you exceed that capacity then that is probably why your floor jack is not lifting. In such a situation you need to reduce the load or find another floor jack that is capable of lifting the object you are trying to lift.
Another most common reason why floor jacks fail to perform is that the oil levels are not at the optimum level. Too much or too little oil, both can cause the floor jack to cause problems when lifting so make sure that your floor jack has the right amount of oil, which the quarter of the oil reservoir. In order to check the amount of oil all you need to do is take out the oil fill plug and then take a look into it, if the oil is too much then take some out of it.