A lot of times when you take them out and hook 12volts to them they will seem find until you take all the time of putting it back in there, only to try and start it and nothing, then you learned that you wasted your time and you get to take it out and put another one in there. A local gen repair shop should be able to test it and fix it for you. Depending on what kind of starter you have now, you can get much better ones to make it start a lot faster. I got a Nippo-Denso and it spins over really fast and starts up quicker than my 6.0L, even when freezing cold outside. Some people really love the mitsubishi starter but the one I have seemed a lot easier to install than the mitsibishi one that I took out.
