The oil light comes on, if the oil pressure switch senses a loss in oil pressure. The first step is to check for oil level on the dipstick. If the oil level is ok, then check the oil pressure sending unit, if the oil level is low add oil to proper level. Sometimes, the oil pressure switch or sensor goes bad activating the oil light on the dashboard. When you remove the oil pressure switch if you see it soaked with oil, replace the switch. The oil light should come off. It it doesnt then you need to test the oil pressure with a pressure gage, which should be 10 psi at idle and 60 at 3000 rpm, by hooking up the tester where the oil sensor lives. If the test does not meet the above, there might be an obstruction in the pick up tube, or the engine main bearings are worn out. Simply your engine is worn. Oil pressure is not generated by the oil pump, but by the clearinances between the moving parts of the engine, particulary the main bearings, cap bearings. The oil pump only moves volume. If this is your problem, the im sorry because your engine needs to come apart. I suggest a remanufactured engine instead of overhauling because the costs are high. One from a salvage yard already tested or in good decent condition.